I do marketing work in my present job and love it. Thought I'd chime in and offer my thoughts - they are free, so take them for what they are worth!
First off, I agree with previous poster about checking on copyright infringement. Nothing says "welcome to business" like having your ball sack sued off and having to cease operation. Find an attorney friend and make sure you are safe.
If you are safe, then I would start with local ways to get attention on your product. Don't know where you live, but even my dinky-ass town has concerts, tattoo conventions, expos, etc. You want to get in touch with the folks that direct or manage those events and get them to let you set up tables, selling your shirts. You could even do this in surrounding areas/towns/communities, if applicable. Once you begin to develop steam (and sales), then you can approach other outlets - like the idea of approaching a major t-shirt vendor. Show them proof that your product sells, and offer them variety and a good pricing arrangement, and go from there.
Hope some of that helps. Not an expert!
P.S. An after thought occurred after looking at your first post. You need some pics of attractive people wearing your shirts. A photo shoot with some totally gorgeous women is a must! No offense to your friend, but his mug isn't going to get my attention!
Last edited by Jim1970; 09-28-2012 at 16:33..
Reason: To add more info