Old Tees

There hard to come by, so when you do come across one you better not let it escape. I'm talking about super soft, worn-out, perfectly fitting old tee-shirts. They are the best and I always seem to have only a few at a time. Most of the time they end up lost or they shrink to nothing. I really want to know the magic behind keeping a tee from shrinking and getting it super soft. Is it just fabric softener? I'm one of those woman who is still learning the tricks of the trade when it comes to household chores. I'm not necessarily interested in learning them all, but learning and perfecting the soft, old, worn-out tee-shirt look is a goal of mine. If anyone has knows the trick then please be my 411. What kind of fabric should the tee-shirt start out as, 100% cotton? I've gone through plenty, but most have been hand-me-downs or have been thrift buys. Right now I have an old yellow-orange tee on with a picture of Speedy Gonzáles' face with "Mamacita!"written in bubble letters under his smilingly face. Very random, yet very original, fun, and comfy.