How to buy/register a used scooter?

Hi, I'm planning to buy a Honda Ruckus, a 49cc scooter. I have never bought a car myself so I don't exactly know how to buy a scooter either. I'd be buying it privately off craigslist.

When making the deal, is there a title involved? Is that the same thing as Certificate of Origin?
Do I collect a proof of registration?
I also heard something about a Bill of Sale, what is that?

Basically, what paperwork should I collect when I buy the scooter?

Depends some on the state of residence. 49cc Honda Ruckus here gets 'Moped' plates, couple other states a 'Moped' that size doesn't require a motorcycle license or any drivers license- and Arkansas for that size I was told was 'title and plates, driver license' optional. Honda Ruckus has good rep, is stolen on campus occasionly and used as a dirt bike. Some dealers in a few states have the little offroad package- tire and bash plate, etc and sell them as offroad, no title given and in a few cases legally. Couple states like New York have or had the registration with bill of sale for purchase, sort of combined registration acts as title with inspection and tax for non commercial use vehicles. Get to state DOT./DMV or stop at local police station for further info.

Verify that the seller is who they claim they are. Know where they live so you can go back to see them if you find out that they are crooks. He signs off the Title. Don't know like one looks? Look up images.google.com and see how it looks. You take the Title to the DMV and they give you a new Title that says it belongs to you.

You are both clueless? You both go to the DMV and learn -- they will have no problem teaching you how it all works.