We just bought a car off of craigslist last week and have bought and sold our last five rounds of cars off of CL. It sounds like I am in the minority, but I would much rather buy a used car from the original owner and have a chance to meet them and check them out than buy from a dealership when you have no idea who owned the car. It actually took a month for me to find a car this round because the good ones were selling so fast. Usually I would respond after it had been posted for just a few hours and they would already have a buyer.
Also, last year we sold our 14 year old Civic and the person who bought it was buying it to resell it at a dealership. So, just because you are buying from a dealership it doesn't mean it isn't a craigslist car.
Here's what I look for:
*Original owner ONLY, with service records
*Clean title
*Responsible looking sellers that hopefully didn't drive too crazy
*I always have the car checked out by a mechanic before buying. I have done this with every car since I was a teenager and I have not yet encountered anyone who has denied my request. I recall two specific times that the mechanic told me not to buy the car. I spent $100 on the inspection, but it was well worth it to avoid a lemon.
*Check KBB and make sure you are in the right range
Good luck!