advice for hitting up a dispensary

so for one reason or another i cant go into a dispensary (the obvious reason) any advice like should i ask someone going in or someone around it? its near a gas station i think maybe someone there idrk any advice helps ik i should give a generous tip and what not. also its in a colledge town so idk if i should give ppl my money before hand but it probably is best to. also would it be to much to ask someone to get me 7 grams of flower would it make more since to ask for prerolls, sry for the anxiety its my first time hitting up a dispensary i knew a guy in sd but i moved away so anyways thanks