How do you know someone is selling weed?!
ask around i get my weed in parking lots just hangout there wear a rock band shirt and you wont believe how many people you run into at least i do in cali
Start up a conversation and ask casually if they party. If they do this should get the ball rolling on finding out if they sell it or not. otherwise ask them if they know where you can get any.
You gotta ask around. You can't be shy. Make alot of friends who seem like stoners. You will realize that it's actually pretty easy.