Many tutorials online, this is just one of many.
http://quiltbug.com/articles/Tshirt-quilts.htm
Also do a search on this board for t shirt quilts and you will have plenty of inspiration and advice. Happy sewing!
edit: I know many people do not quilt thru the screen printing on the front (block) but I do and have not had any problems. If the blocks are small some tie instead of machine quilt.