I'm a poor college student so I keep it slim. I check websites often, this way I know what hits the shelves on any given week (I have to stop looking at the previews!). Right now the average amount I spend is $3.40 a week - Needed something to do in class today! I stick with titles that are going to be fun, suspenseful, interesting, funny, and just plain good. The books I pick out now are:

Action Comics
Superman
Adventures of Superman
JLA (Good Stuff)
Amazing Spider-Man (Fun and hilarious at times)
HERO (*NEW!*)
Masters of the Universe (Maybe)

My interest in Superman has gone down a bit, I'm interested in the Zod and new Supergirl stories. The Obsidian Age had me loving JLA, and Amaz. Spidey has been really good since JMS hopped on. I'm saving up for trades, they're good for travel.