Doing graphic design and doing graphic design for printing is not actually the same. Sometimes we get different outcomes, and we always need to make sure that a printing company prints the same one that we want to have.
The article gives a guide of graphic design for t-shirt printing. First suggestion is using PMS colors to get more accurate colors with a silk screener, and the article includes a link of how to use Pantone in Illustrator. Second, the text needs to be changed to outlines so that the artwork can show the text as an image. Third, we better use the actual size of the printing. Forth, vector artwork can makes the print cleaner. Fifth, the strokes need to be expanded. Lastly, using half-tones will save the amount of colors and may reduce the budget.