Honestly it depends, sometimes I'd ignore them (almost always ignore the ones sitting on the sidewalk) and sometimes I'd give a few bucks.
EDIT: I remember this one beggar on a trip to Florida when I was like 12, he was awesome, I wish I had given him more, he was this thin African American with short bushy hair, we were at the Stadium watching a basketball game and one of the teams scored over some arbitrary point number so on the way out people could get 1 free taco coupon for Jack in the Box from one of the employees standing at the door, I managed to grab about 25 without the usher noticing, and on the way out this beggar, totally upbeat and polite, was asking not for money, but for the coupons. I shoved all 25 in his cup, the look on his face was priceless, he just looked at me and said in an upbeat tone: "Children are our future!" Really nice guy.
EDIT: I remember this one beggar on a trip to Florida when I was like 12, he was awesome, I wish I had given him more, he was this thin African American with short bushy hair, we were at the Stadium watching a basketball game and one of the teams scored over some arbitrary point number so on the way out people could get 1 free taco coupon for Jack in the Box from one of the employees standing at the door, I managed to grab about 25 without the usher noticing, and on the way out this beggar, totally upbeat and polite, was asking not for money, but for the coupons. I shoved all 25 in his cup, the look on his face was priceless, he just looked at me and said in an upbeat tone: "Children are our future!" Really nice guy.