Does EVERY song on it have to be a hit?
No. Sometimes this is more of a turn off to me than an attraction.
Are 3 or 4 quality songs your standard?
I'd say over half the CD, at the very least.
Does it have to find a way into your everyday rotation?
No, but if it's good, it does!
Does it have to have at least one hit/quality song?
See above (over half).
Does it have to have songs that chart on the Billboard Top 40?
Absolutely not. Those are some of the worst songs out there, IMHO.
Usually I like to hear at least 3-4 tracks to get a sense of whether I like the artist's sound or not. Once in awhile I'm very impulsive if I hear a song I like. Sometimes I get burned that way (Villians by the Verve Pipe comes to mind). Other times it's great (Bowling For Soup after hearing 1985).
Like Darren, there are some bands I go after without hearing a note. Anymore, that list is down to Green Day, Goo Goo Dolls, Styx (new albums only, not compilations), and Weezer. Def Leppard used to be on the list, but I didn't care much for their last album.
Finally, once in awhile I'll buy a CD of a band that's coming around in concert to help me decide whether to go to the show or not. I will also sometimes buy a CD at a show if I like the concert.