Level Change
Question for you guys. I've made three maps,and I'm using trigger_changelevel and landmark to change maps between them
But, the areas change rotation. In map 1 you enter an elevator from the east, then you exit north in map 2. Because of the rotation, I'm being dropped out of the world.. is there a way to have it rotate directions or something? so that I spawn inside where I'm supposed to be?
Or do the parts of the map have to match perfectly? even if I rotate the landmark and trigger_changelevel?
I think the maps have to be exact. Try messing with the orientation and other properties of the info_landmark in one of the maps to see if you can force a rotation. If not, try physically rotating the map.
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I had this same issue. I'm working on a set of maps at the moment and didn't realize that when you do a level change the elevators have to be facing the same direction in each level. I searched for quite awhile trying to find a solution, but the only thing I could come up with was rotating an entire level to get the elevators to match (select all -> transform -> rotate on z axis -> fix all the doors in the level to open the right direction.)
Also, if you're falling through the world, be sure your landmarks are in exactly the same place relative to the elevator shaft in both levels.
I, too, had the same problem. If the front of the elevator is facing right in the first level, the front of the elevator in the second level must also be facing right. And the landmarks HAVE to be in the same spot in the elevator shaft. The best way to ensure this is to copy and paste the elevator and shaft from level 1 to the start of level 2, but move the elevator up to the top of the shaft. (where it stops.) This may sound confusing, but after you tinker around with it for a while, it will come to you.
Waaaauuuughhh!!! don't do that! 
make sure all your brushes are aligned to the grid! something could throw your brushes off grid and create lots of problems! and rotating everything doesnt always rotate the angles of entities, so you may have to (or have had to) rotate your entities. just be careful 
Yeah, I'm going to have to move the elevator. if I tried to rotate my entire map, I'd have to go around fixing a LOT of stuff. I know in map 2 this wont be too much work, but I havent looked in map 3 yet.
Ok, I've moved things around and got myself appearing in the right spot.
Now I've got a NEW problem. My elevator is within the trigger_changelevel and is being transferred to the next map WITH me. but its not tied to the elevator in the next map, so its getting me stuck. what the hell!?
.... 
oh god. I just took a look at the demo map, and they have the entire elevator surrounded by a trigger_transition.... meaning they transfer all the freaking entities to the next map...
Is it not f'ing possible to transfer JUST the player?!? if so, how?
Remember to make the landmark names EXACLY the same, including capitals, _'s and so on.
Also you HAVE to have a change level brush in your map even if you don't want the player to change maps.
Also you HAVE to have a change level brush in your map even if you don't want the player to change maps.
all the names are correct. I have a change level brush in both maps, I even tried moving it up above the elevator into empty space, and it still takes the player, and everything else.
Unless you use a trigger transition, all non-static entitys nearby to the changelevel will be transfered to the next map.
You may not be able only transfer the player to the next level. I was thinking you might be able to use a trigger_transition to surround only the player, but that depends how a trigger_transition selects entitys (is it based on an entitys origin, or whether it's completely inside the trigger, or whether it's partially inside the trigger? not sure.)
Honestly, I would try to set it up as much like the demo level as posible. It takes a bit of work, but once it's done you can pretty much just copy -> paste for future work.
Oh, perhaps you tried moving the landmark's origin instead of the actual entity, make sure that you did this correctly.