I'm in charge of getting new tees for our agility club and I have no idea how to start!

I mean, as far as how to design a new logo for us. I'm going to call the shirt place on Monday and I'm sure they can give me some pointers but since I have a long weekend I thought I would get a jump on things by looking at clip art or something.
Anyone have any pointers?? Anyone does this type of thing before? I've tried googling "agilty clip art," "agilty images," "dog beach images," etc. with not much luck.
