I'm thinking of buying a used vehicle, probably a Honda CRV or Toyota RAV,
mainly because of their reputation for reliability, decent gas mileage, and
a certain (if limited) ability to handle high-clearance dirt roads.

My question is not so much about these particular models, but about any
advice anyone cares to share about the buying process.  Not caring to go
through all the stupid and frustrating salesperson games on a car lot, I
intend to buy from a private seller.  However, I'm sure this method has its
own risks.  For example:

How high is the risk of some sort of fraud--e.g., someone selling a stolen
car with a forged title, or other such things?  And do used car salesmen
often pose as private sellers?  (I once had a neighbor who sold a different
car in front of his apartment every month or two--seemed quite suspicious.)
Are there any red flags of seller behavior to look for that will alert me to
the possibility of the car having problems, a shady history, etc?  Are there
websites that give advice on the buying process?