/vr/ - Retro Games

So I'm making a map and while I'm learning the basics of mapping, before I get down to the serious work I'd like to ask a few things of you guys.

>What makes a good fight in a map?
>What helps set up the atmosphere?
>What are some things you think are just plain bad and should never ever be done?
>Anything that is overdone?
>General comments or tips?

You dont have to, but if you can point to some examples in various WAD's of good or bad that would be alright too.