make him show you some id, pat him down make him move out of his area, what's the rush, ask him to come with you to a favorite bar and have a few drinks with him, don't deal on the first meeting exchange phone numbers with him and build a relationship. Remember cops are ASSHOLES and their job is to put you in jail, and teach you a lesson, he's going to want to move you along and get back to being an asshole and teaching you a lesson, pretty quickly and doesn't have the time or inclination to slow it down and get to know you, if you should get to know anyone it should be the guy you are buying from.UHhhhh.....lets see....tips to avoid getting jumped.....
1. Don't do it(wont get jumped or arrested)
2. Bring a weapon.....if its 5-0 then you get "aggravated" added to every charge.
3. If you don't know what you're talking about atleast act like you do....less likely to get ripped off.
4. Bring a friend with you just incase.....let him wait at a safe distance as to not scare the guy you're meeting off if hes a legit reliable hook up.
Thats about all I can think of....good luck to ya