Stop buying Abercrombie & Fitch vintage T-shirts. Have you noticed you have on the exact same thing everyone else around you has on. Not to mention that they are overpriced and boring.
Major corporate stores are great for some of the basics like jeans or undershirts, but you t-shirt collection should be something personal and not a function of what goes on sale at the Gap.
The truly great vintage tee comes from finding the one great shirt that you stumble across in your parent's old wardrobe or at a garage sale. There are great finds to be had in every thrift store. You never know what classic shirt has been tossed away by someone with no appreciation for pop culture. Hit up some thrift stores and cruise through the selection. You will see a lot that doesn't work but the one great find will set your wardrobe and sense of style apart from all the rest.
Other goldmines are vintage record stores, and flea markets. You should be looking for something that appeals to you and is a one of a kind. There are plenty of great finds out there just waiting to be discovered, and if they don't work out you are only out $1.50.
Always be on the lookout for classic concert tees. Even if the band sucked at the time it is now vintage and it will make your parents feel old. Also keep an eye out for any company or logo that was popular in its day but has been phased out. Just like classic cars, these will never go out of style.
However you go about finding your wardrobe try to be original and breakaway from anything that everyone has either already found or can buy when it goes on sale. Your clothes say a lot about you so make sure to add your own touches.