T SHIRT 101. I know the t shirt making game is huge now. Everyone is a fashion designer. But do you know what you're doing? Thankfully, I've been doing this longer than I've been doing GR, so here's a simple tip. Make your design. It could be good, it could suck. I can't help you there. But follow this easy step.
Print the thing out. If you have a color printer that's great. but if not, then make it on a white shirt, and print it with a white background. Print numerous sizes of it, and figure out what's going to work on a Large, Medium, and maybe small. Then print another one for the girl shirts. Try to have blank shirts in the sizes you care most about. Size does matter when making your shirt designs, do don't assume this step is easy, it might be the most important step in making your design look right. An important tip is to cut the design out from the paper, and tape it on. I'd even have someone wear the shirt with the design on it.
This is hwa-shi starting to cut up his design. This is going to be for GR. He didn't want to print it out first to check it. I told him he should. "No one listens to the publisher." He may not do this step again, and he'll pay for it one day, but not on my watch.