I've done it twice.
1) Get someone to give you a bill of sale and get it notarized when they sign it in front of the notary
[I'll do it if no one else will, but I can't notarize and I don't have a local bank]
2) Get this:
http://dmv.vermont.gov/sites/dmv/files/pdf/DMV-VD119-Vehicle_Reg_Tax_Title_App.pdf1A: New
1B: Motorcycle
2: Do all of this
3A, 3B: Skip
3C: do this
3D: skip
4A: do this
Where it says VT Driver License No,
put your Missouri Driver License Number. This is very important.
Personally, I put mine and then put [MO] after it.
4B: skip
5A: skip
5B: Name/address of your notarized bill of sale
6A: Put purchase price that is reasonable and then also put the tax of 6% at the bottom
DO NOT PUT $1 or whatever. They will charge you the fair market value lowest price and send the application back if you put a number that is too low.*
If possible use Blue Book or something "official" because that's what they use, and they will charge you
6B: Blank
7: Blank
8: Sign and date
9: Go to their website and figure out the fees.
Again, if you fuck this up, they'll send it back to you, hopefully with the correct numbers. So don't sweat it.
* Which is okay if you're not in a hurry, then you'll know the minimum to put. But at 6% for a moped the price is so low it doesn't really save you a lot.