Well, that's a tall order, but I'll give it a shot.
1) Don't buy just any locker because the price seems right and no one is bidding on it. There's a reason for no bids.
2) If you see a hint of collectibles (sports, entertainment, die-cast cars, etc) it MIGHT be a good lkr.
3) Photo equipment does well for me.
4) Brand name tools would be good (Makita, DeWalt, even Craftsman). Taiwan, no.
5) See a possible gun case no one else sees? Go for it. Might be empty, might not be a gun case.
6) Hi-end furniture good. Particle board no.
7) TVs are good if plasma, lcd or LED. Old ones not so much since most won't be digital.
8.) Clothing (for me thats Pro Sports Jackets, leather jackets, name brand tennis shoes, good boots)
9) Comic books...Superman #1(Like the one Nicolas Cage owns...valued at millions.)
10) Vintage nudity either in old Cavalcades, etc or original b&W or color prints of what were then called "nudes".
OK, now for the flip side...what you will actually see:
1) stained mattresses
2) dressers missing drawers
3) waterbeds (frames and MAYBE the bed itself) (no Posturpedics probably)
4) old canned food (bulging) old noodles (mouse chewed)
5) transparent containers (like 2 liter soda bottles) with 3" of urine.
6) other goodies list the other members here will provide for you.
Go get 'em !