I use various methods depending on the gametype or theme (my favorite word). I have never once tried to draw layouts since it's harder to manage smaller details.

If it's multiplayer, I usually get some random idea pertaining to the look/theme of the level which sort of works like a 'seed', then I'll create it in jcs and hope for the best. If I like how it turns out, then I tweak it to get an idea of how the overall gameplay will reflect the personality of the level, and everything falls in place from there.