Hey,
I'm going to look at a new car (new to me at least) tommorrow. It's a 91 Firebird base with the 3.1l. I know it's not in the best of shape, but are there any red flags or particular things that I should watch out for before buying it.

 

Do you know anything about it beside engine size? History, recent repairs, stuff like that? How much is the seller asking for it? Does seller have a title? DO NOT buy anything without a title. That's just asking for trouble.
Off the top of my head, check tire tread, look for puddles, make sure you run the car til warm, make sure it doesn't overheat. Check for puddles again, things can start leaking after car is warm. I personally would bring a vacuum gauge and see if there are any odd readings.
Make sure you can test drive the car. If seller won't let you test drive, walk away. He is probably hiding something. While test driving, watch for smooth shifts and listen for strange sounds, ticking, etc.
Check all fluids. Use your nose. you can smell problems that you cant always see right off the bat. if fluids are low, trans fluid smells burnt or is overly dark, coolant looks bad, it means this car wasn't well maintained and you should probably count on problems in the near future.
I would get a carfax report. they cost around $20 but they are very much worth the price. If everything checks out, still take it to a trusted mechanic and have it inspected. It only costs $50-100 and believe me, it is worth it if they find anything seriously wrong. that's from personal experience.
Do you have any experience turning wrenches? These cars are often abused, and if you don't know how to fix it, I can't reccomend you buying it. this is a 21 year old car, stuff will start breaking sooner or later. just be prepared for that.
I hope everything works out for you and keep everyone updated on what you decide. welcome to TGO!

 

Also, make sure he hasn't warmed the car up before he starts it for you. If possible go in the morning when it's a little cooler out. Some problems are more apparent when a car is started cold. ticking, smoking from leaky valve seals, stuff like that are all more apparent when it's first started cold. Ask the seller to wait to start the car until after you get there. if it is warmed up when you get there after you ask him to wait, then he may be trying to cover something up.
here's a website I found that looks pretty useful as far as finding what to look for.
http://www.samarins.com/check/simplecheck2.html
also just did a quick search and found what looks like an excellent checklist to follow.
http://www.popularmechanics.com/cm/p...-checklist.pdf