As I'm sure you have read, countless busts have gone down from cops following people from hydro stores, or worse, hydro store owners ratting on clients.
You already have the basics down-
1) drive a car not registered to you
2) take order to a random house first
Those are the two big ones for sure. The other obvious ones are pay in cash, first names only with the Hydro owner, and most importantly, don't fall off the bandwagon. What I mean by this is some people will do the precautions for the first order but then when they go back for supplies they get lazy and take their real car and go right back to the grow from there. Don't do that.