One of the most common problems people have when editing arise when compiling. Usually cryptic errors from vis or QBSP that seemingly take forever to track down. Most of these could be solved before they happen with a little knowledge and applied technique. By following a few simple guidelines you can limit most of these errors, and make faster and better looking levels.

When building a level you often have to create something to put in the room which requires some difficult brush manipulation - subtraction mostly. A good way to do this is to open up another map and do your work on there. Say you have to build a lamp fixture. You would open up a new map and work there to build it to match the dimensions on your main map. Here you could perfect the lamp until it is exactly how you want it and then when it's complete and error free just group it, copy it, and paste it into your main map where it goes. This will ensure that the lamp won't be the cause of any QBSP errors. No waiting for 20 minutes for QBSP to come back with a "clipped portal" or "duplicate plane" error. Also, with the registered version of Worldcraft you can make the lamp a prefab object for greater conveniance.

Another common technique is to build a level one room at a time and then to copy all the rooms together on one map once they have individually been tested and are error free. Remember, with both of these methods texture alignment comes after you put everything in place as textures will become unaligned once they are moved.