I'm a new rider, too, and I just bought my first used bike.
Here are the steps I took:
* Find comparable sales in your area on eBay (not Craigslist). Print those out and bring them with you. I bring a binder with me.*
* Make an inspection checklist when you view the bike. Mark down everything that doesn't pass, even little things (tears in the seat, old tires, etc.) and point them out to the seller as you find them.
* Be upfront with the seller: tell him you want the bike, but the average used price in your area is X, and you found issue Y that will cost Z dollars to fix, so you're ready to offer X minus Z.
The Cleveland Moto Podcast had a fantastic episode on how to buy a used motorcycle. I wrote down their advice and posted it here. If you like I can PM you the print friendly version I took with me while bike shopping.
Good luck!
* In my binder: comparable sales, my inspection checklist, and blank bills of sale.
I would not sell a bike to any dork that attempted this crap (lol @ binder).
then
and
and probably too busy
to kick your ass out of my garage.....but that would be the end of our conversation. 
+1, sorry guy. Glad someone was nice enough to sell their bike to you.