Not much to add here except to reiterate discussing the trade after you are happy with the price you have negotiated on the car you are buying.
Also, I have never taken the trade-in car to the dealership with me unless I've gone over it with a fine tooth comb. I'm talking a bumper to bumper cleaning, especially the interior. I get it looking like it just came off the showroom floor. After that's done I wax the crap out of it and put that tire-wet stuff on the tires. This all takes a couple of hours but I've found it to be very well worth it as I've always got what I wanted (and sometimes more) on the trade-in. (Like many have mentioned, I would much rather do the trade-in rather than dealing with Craigslist idiots.)
I even had on car salesman say "Your truck is so clean we could eat off it."
Also, I have never taken the trade-in car to the dealership with me unless I've gone over it with a fine tooth comb. I'm talking a bumper to bumper cleaning, especially the interior. I get it looking like it just came off the showroom floor. After that's done I wax the crap out of it and put that tire-wet stuff on the tires. This all takes a couple of hours but I've found it to be very well worth it as I've always got what I wanted (and sometimes more) on the trade-in. (Like many have mentioned, I would much rather do the trade-in rather than dealing with Craigslist idiots.)
I even had on car salesman say "Your truck is so clean we could eat off it."