Originally Posted by d-null

fair enough, always something new to learn for all of us

if I were you I would contact the t-shirt screening company, show them the logo, and ask them what would be the best route.... the photoshop methods that are being used in this thread so far are not the best way to go for this

any good designer would be able to knock off your design exactly and in illustrator which would give you the flexibility to scale perfectly to t-shirts or even billboards if you needed, and the design you have should probably look best adapted to a 3 color spot color rendering, that will look most vivid and beautiful on a t-shirt, whereas a cmyk 4 color print of it would look duller