Belt Tension

I changed both belts on my car the other day. It's a 1993 Mustang LX Hatchback, 4 cylinder. My step dad had a fit cuz I did it with a neighbor rather than go to our mechanic. Now he says the belts may be too tight yet everyone else tells me the belts are self adjusting as far as the tension goes. I don't have a license or a tag on my car yet so I can't drive it to the mechanic. I do not want to burn out the altenator, p/s unit, or water pump. Nor do I want to burn out the a/c compressor either. This is my first car and I want it to be right. I would appreciate any advice you can give me.