Well, I'd suggest finding one dealer, then use him above everyone else. This way, you'll find that he gains faith in you coming back, and also puts his prices down for you, cuz you're his 'special costumer'.
If he's not avaibable, however, find a user who always seems to have some on him and simply ask: "Would you like an extra buck?"
-- Or just grow your own plant.
-- Or just find other dealers.
-- Or just quit smoking (disregard that one, sorry :-P)

It's so easy to find weed if you got the will. Just build on your natural stoner instincs :-)