What are the ideal requirements for pictures printed on a t-shirt?

Question:

What are the ideal requirements for pictures printed on a t-shirt?

I'm drawing a picture to be printed on one of my school's club, which will be sent to the t-shirt making company. I'm drawing it on adobe. And I'm wondering maybe it's a good idea to make the lines thicker and what size should the picture be? Bigger for better quality? maybe be 1/2 times better than what it should be print on the shirt.
Anyone expert in t-shirt printing area help?

Additional Details

6 months ago
No one answered, you guys are mean, lol.

Best Answer - Chosen by Asker:

Space on a shirt is about 8 x 10, so use this for the deminsions.
300 dpi is enough. Are you using screen printing or heat transfer?
Are you getting the same sizes throught of different?
If you get 20 small, 40 medium, 50 x-large, etc.
Just remember that the size printed will be on the smallest size shirts for screen printing because its one screen print on all the shirts.
I work for a print shop, they have great prices with free shipping.