private sale, do not pay a deposit...I wouldn't pay it, you have no easy recourse in case something goes wrong. Like others have said, you need to instill confidence in seller that you're not flaking out, that's it.
Let me get this straight, you're GOING there to see, test drive, and buy the car right? Please don't tell me you're paying it first, and then having the car delivered. If so, this is the oldest scam in the book.
Just arrange a meeting time and place, take your checkbook with you or a deposit slip. When everything checks out, go to your bank with the seller, and do a inter-bank transfer, the teller will confirm funds, and then it's done. No risk on seller or buyer side.