Most of my car buying tips you probably already know. Don't take on a car payment, get a vehicle history report (horror story on not doing that here), etc.
Here's the tip that most people don't know about: Use Consumer Reports to determine a vehicle's reliability.
Consumer Reports is a magazine turned website that gives ratings on every product you can imagine. Once a year they put out a "Auto" edition that has literally thousands of car models with rankings. (You can purchase an online subscription to view their information, but I've gotten by with a library copy of their magazine anytime I need it.) The most important thing they rate is a vehicle's reliability.
The thing is, no one person can possible drive enough vehicles to know which ones are reliable or not. Yes, there are more reliable brands (like Honda or Toyota), but even they have some clunkers mixed in at random. Consumer Reports gathers thousands of users experiences and breakdowns to give an overall reliability rating on each vehicle.
As I'm car shopping I look for cars that are above average reliability. I have yet to be let down or find Consumer Reports to be wrong.
One story: We were given a vehicle by a member of our church with an average reliability rating. Not only did it die sooner than any other vehicle I've owned, it also had issues in the areas Consumer Reports observed: electrical and major engine. Could be a fluke, but I doubt it.