Start with your local elementary school, then work up and down from your local elementary school (the elementary school is typically placed at the center of a given town section). The trick with driving for dollars is having a pattern to follow.
Do you have a script if you meet a Seller? What things do you look for that make a property attractive to you? Do you have a package that you leave behind when you do find a vacant property that is attractive to you?
Having a script is critical, you may never get a second opportunity to pitch a Seller, so I highly recommend assuming that you will run across a Seller and will have to pitch them on the spot.