How to buy a used car?

I’m looking to get my first car, and have been doing months of research and choosing to figure out exactly what car I wanted. I’ve finally come upon something sensible, practical, reliable, and also fun and decent looking.

I’ve taken a year of automotive mechanics at a trade school, and have worked for family members and friends doing things from tune-ups to engine replacements. However, I will admit that I don’t know quite all of the possible problems yet. I’ve learned a few very common things to look for, but not everything. I joined an enthusiast forums for the car I’m wanting to get (a Nissan 240sx), and have been reading up on what problems they have. I’ve also been talking to current and former owners of these types of cars to see what their opinions are. So far I like everything I hear.

Since this is my first car, I’ve not had any buying experience yet. I plan on taking a family member and my former mechanics teacher with me, as well as a diagnostics scan/monitor tool.
However, since I’m looking for a specific kind of car, even down to the options and color, I figure I may have to travel a couple hundred miles to find one available or at a reasonable price. The problem with this is that, while I can still take the family member(s) (one who is quite the mechanic himself), the mechanic teacher may not be willing to travel just to possibly find it’s a bum deal.

My main question is this: what, other than taking someone who knows more than me, getting the car scanned, test driving it and similar cars to get a feel for them, and getting a CarFax, can I do to ensure I get a good deal?