I'd like to add a couple of things to Harpos great suggestions...

1) Don't have a buddy just standing around ya... It make you look desperate...
2)On the subject of the eye contact, and hope thing... Ya.. you can hope... you can smile, but DON'T be an ass to people who just walk by, even if they make eye contact and smile back at you... You are essentially BEGGIN and beggers can't be chosers...

I was downtown last night and saw a busker break both these suggestions... The chum he had just standing beside him smoking and looking gruff was off-putting enough... I decided I'd give him a miss (besides, he had great shoes... No busker whop really needs the $$ has great shoes!) But not to be impolite I met his eye, gave him a smoke and a nod of my fedora by way of encouragement... as I was passing him by i realised htat he was actaully pretty darn good, so I though I'd 180 and toss him a couple of bucks... before I could turn I heard from him "fuck you very much"

Not only did I not give him any cash, but I was sore tempted to kick his scrawny, too-big-pants-wearin' ass all up and down main street...