Congratulations, you've started playing on KoR servers. The mods and admins take the effort to make the game fun to play, and it is. Just like in default Tremulous, base building is an important part of how well you do. Layouts is the special KoR server dedicated to ATCS and, you guessed it, layouts, which while not always fair, are a fun challenge to try. Before you start building, take note of how KoR servers have special settings:
Game speed is higher. This means you can traverse the map much quicker, and do jumps that you couldn't do before. However, buildings still act the same way, so turrets cannot turn as fast, buildings do not do as much damage, etc.
Gravity is lower. It does not hurt as much for humans when taking big leaps, and maras and dragoons can go a long way in the air. Also, jumps go farther.
Total build points is much higher (150). This means you can build more complex bases or forward bases, and buildings which are sometimes considered superflorous are now better to use.
Friendly fire is off for buildings, and pounce/charge does not do team damage. Human bases will now not die to a newbie nader or luci-user, and it's very easy for dragoons and tyrants to run across the map.
General building principles
Ok, now on to building techniques. It's highly suggested that you've read the building guides on the Tremulous forums. http://tremulous.net/forum/index.php?board=11.0 Know that humans start out with much better defensive buildings than aliens, but aliens have much better units. In stage 2, humans get only the defence computer, but a helmet, more energy weapons, and a jetpack, which greatly augments their offensive capabilities. Aliens get trappers, which should replace nearly all the acid tubes you have. They're very nice, slowing down base destruction more that acid tubes would in KoR. In stage 3, both teams simply get an uber-weapon.
Human bases aren't much different from before. Generally, you want the RC in the farthest corner from any approach, 2 telenodes near the back, 1 armoury that has relatively easy access, 1-2 medistations near the armoury, 1 defence computer if you're stage 2 or higher, and a ton of turrets, and if you want, some teslas. Defence computers are much better in KoR servers even with only turrets; there are so many more turrets to split up targets between. Try to build buildings together; with increased speed, it's very easy for any alien except grangers to kill a lone turret, and maras and up can handle groups of 2-3 turrets. As always, buildings are useless without defence, so keep on the lookout for aliens trying to ambush your buildings. If you're building a forward base, always keep it defended. You only really need a repeater+medistation; forward bases are for attacking the enemy's main base, and energy weapons are simply better than physical weapons for that (other than painsaw versus stage 1). This is also a really cheap base, costing only 8 build points.
If you're building in either colored room, I suggest having the RC in the corner of the room where it is in default. RCs are really bad at killing aliens; they can only damage 1 alien at a time, and the damage to an alien on the top is only 2 per second. Build two telenods near the walls next to the RC, along with a defence computer, and build an armory and 1-2 medistations nearby. Try to create an arc of turrets surrounding these buildings; this makes it so that enemies have to take damage from basically all the turrets when they try to attack the turrets with melee. With your spare build points, you can build turrets overlooking the edge down to the main entrance, or near the ramp to the RC. Remember that tyrants can jump across the middle area now, so try to position any turrets that you place in front so that tyrants will most likely fall to the middle area.
If you're forced to build in the bunker, put a reactor in the back of one of the 2 areas, next to 2 telenodes. The armory and medistation(s) should be not snipable from outside; either build in the back next to the RC, or along the inner wall, near to where the stairway to the ceiling on the outside would be. Build an arc of turrets to protect these buildings that cannot be sniped from anywhere except that leg of the bunker; then, build another arc of turrets that cannot be sniped except from inside some area of the bunker. Then you can build extra turrets as you wish. It's inevitable on this map that you will need to jump to exit/enter your base.
The only real alien base that can stand up to repeated attack is in either colored room. Build the overmind in the corner of the platform, and 2 eggs nearby, 1 egg in another corner of the room, a booster, and defensive structures. The principle of post-s1 building is spreading buildings out so they don't get taken out together by splash damage. In stage 1, build acid tubes in clusters, and don't let humans shoot them from long range. In stage 2, replace most of these with trappers. In stage 3, build a hovel (which is free) on top of the gap from the main entrance to the platform with to OM to stop luci jumpers; it should be slightly over the gap. I wouldn't suggest building a hive, except maybe on the ceiling of the area where the OM is. Hives need a line of sight, and that's the only area where it can be and not get immediately shot at by smart people. You really don't need a forward base; aliens travel fast enough to get to a booster in the original base, and humans can quickly destroy a forward base anyways.
Specifically, build an OM in the corner. Build an egg on the ceiling in the corner nearer to the ramp, with a booster below it. Build a hovel in the manner described above, and an egg on the ground next to the wall halfway between the hovel and the overmind. I like having an egg that can't be shot from the bottom along with an egg that can't be shot from area that exits to the hallway. Build trappers in the corners of the small hiding areas on the bottom entrance (specifically, on the top corner closer to the main entrance for each area). Build an acid tube or trapper on the side of each ramp (so that it doesn't block tyrants). Build an egg in the area of the room opposite the overmind near the other ramp, on the ceiling in the corner where it's hard to shoot. Build a trapper/acid tube on the slanted ceiling above the main entrance; if you can, build a trapper so that it shoots to the hall entrance. You can build a trapper on the wall of the boxy area, either so that it is near the hall entrance on the other side and shoots if you look at the boxy area, or perched mostly on air, firing to the very corner of the entire room. You can also put a trapper on the sub-divide on the platform where the OM is, where there's a little slanted area near the ceiling, so that it fires down to the bottom entrance, a similar curved ceiling above the big platform, or hiding on the wall slightly outside the room in the hall entrance.You could build trappers on the far sides of the subdivides too.
Layout specific guidelines
If it's the default layout or with switch positions, humans should simply build a few turrets near the RC, and do some moving around of buildings to be more efficient while you're not under attack. Then, proceed with the base plan. Aliens should build a third egg and some acid tubes on the ramps/next to the subdivide, to prevent people from painsawing the overmind. You can't really build a good base until stage 2 anyways.
If humans have an arc of turrets surrounding well-placed essential structures, quickly get a turret or two out near the edge of the platform. Dretches are harder to hit in the base than they are in the hallway or outside. Then, proceed as normal. Aliens don't really need to do anything until stage 2.
If aliens simply have a ton of eggs everywhere, quickly get an OM up in the red room, decon some eggs which humans can kill for credits, and then build acid tubes around the OM, and continue deconning the random eggs. Humans can follow default strategy. This map is advantageous to humans, but don't feed the eggs.
If there's spawns all over the open area, with an overmind/rc behind their spawns and halfway over the edge, humans are most likely screwed. If you're alien, screw building until they kill your OM. Just go and attack the humans. Humans have a few strategies: build a ton of turrets in the bunker, and then hope you survive when you need to build your RC there. You can also move the RC to the red room and try to survive. To try for a risky but quick victory, build an armoury in a corner somewhere, and try to painsaw the OM and all the eggs (hopefully your teammates will get the cue and kill the eggs). If you're desperate, build in the hallway, and kill the egg there while you're waiting. Aliens very rarely go there.
If there's a few organized spawns outside, but no sign of the OM/RC, it's in the bunker. The first spawn on either side spawns in the bunker. Aliens need to either quickly move the overmind, or try to make so many acid tubes that any human that tries to get in that leg of the bunker dies in less than a second. The acid tube strategy only really works if you hit stage 3 before they hit stage 2, and you kill any turrets that try to encroach there (or hide from them behind acid tubes). If they start killing your bunker base, you should move your OM to a colored room (I really hope you have 1 or 2 eggs outside so you aren't stuck in the bunker). Humans should quickly build in the bunker, maybe even placing turrets that fire on anything that tries to run out from the egg in the bunker. You can probably build an armory and try to quickly painsaw eggs. Decon the telenodes on the outside while doing this, but remember that there's only 1 node in the bunker by default, so build a 2nd one before you decon all of them.
If there's an RC in the blue base, with one node and a ton of eggs around it (or an OM in red base with one egg and a ton of nodes around it), humans need to act fast. (I really hate how OM can damage all humans in the vicinity at once while the RC only damages one.) Humans need to have someone spawn next to the RC and quickly decon it, or have someone rush through the hallway and set up turrets overlooking the eggs. (If you're a dretch, try to go through the hallway to stop this, because your teammates won't.) If you do this strategy, remember to kill the egg next to the OM.
If there's a line of turrets in the red base with 6 spawns behind it, or a line of acid tubes in the blue base with 6 eggs behind it, you simply need to build a controlling structure fast. Aliens should have one person build the OM (don't decon eggs to place it in the corner; you can get a fast victory if you give your team the OM a few seconds faster). Humans need to have one person build an RC and the rest keep the dretches from killing the turrets.
If there's random spawns all over the place, either side needs to get up a controlling structure fast, and notify their team. Don't forget to defend your OM, aliens, or 1-2 naked humans could kill it before it's built and warning you that it's DYING. I've never seen humans try this, but you could have 1 person spawn, build an RC, and then leave the aliens clueless as to where you are. Then start spawning when the RC is complete and start building. Too many humans just feed before there's a base.
Forgis's Layout have 12 acid tubes/turrets in the circuit front entrance to the colored rooms, with vital structures placed in the corners. Unless someone moves, whoever reaches s3 first wins. Aliens may have trouble keeping their base alive when humans are s2, because pulse can do a lot of damage from safe areas before an alien defends. Aliens should quickly move back to the red room, and build from there. When deconning structures, decon the ones which are easily viewable first, including the egg that can be seen from the open area. Also, if you don't want a ton of buildings to die at once, don't decon all the eggs first. Humans should move turrets from the part of the circuit facing the blue room, and build either at the hallway entrance, or on the large platform (concentrate on one area, then do both). Once there are a lot of defensive turrets, decon the rc and move it. (Leave some turrets in the circuit to slow down aliens slightly.) If either team does not move to a colored room, you can even build behind their base.