HELP! busking tips.

My friend and I are a bit short of cash and thougt we'd have a crack at busking (we're 14). We both have steel string acoustics and can both play reasonably well. Are there any tips for songs or stuff for us to play. Neither of us can sing so we're relying completley on our guitars. Also are there tips you can offer on choosing a place to busk and special tricks to increase your chance of money?

Thanks.