THIS POST WILL PROBABLY BE EDITED TO INCLUDE MORE TIPS ETC. SO KEEP CHECKING
I have been flaming waaay too much as well so here I am to try and set things rights. First of all, to try and elaborate more on Paul112's hints, some of which I noticed don't fully explain things. anyway:
1. I didn't know that myself! Thanks Paul112!
2. Cool, I didn't know that either!
3. Sorry to be a perfectionist, but it is 1-6 and pressing enter sometimes places things like a chair halfway through the floor instead of directly on the floor, so use PageUp and PageDown to set this right.
4. To elaborate further: Click File-->Build Game and the build game box will pop up. Click the Level Settings tab and then click the Edit button to the right of the Global Script. Find the Setting named Light Ambience and make it lower to make things darker, or make it larger to make things lighter.
5. DEFFINITELY!
Some Multiplayer Map Suggestions of my own:
1. Set weapons to respawn, but at an appropriate time-you don't want another Player to own everyone else, simply because they have a really good weapon which respawns every few seconds, giving them an unlimited resource of ammo.
2. As opx89 sort of implied, don't use dynamic lights and DON'T use unnecessary dynamic objects. Examples include:
-Dynamic movable terminal
-Dynamic Movable barrels
Etc.
Hope this helps,
Tom