It is a touchy subject, that I usually find hard to deal with. In India, you will be overwhelmed and I guess that most come to a plain NO as a general rule. As others said, especially with kids, although looks harder to do. One experience we had in Pushkar:

A 12-13 y/o kid comes to us speaking quite good Spanish (our language). Nice, friendly chatting. After a while, he asks if we can give him some money. I say: I will rather give you food (he said he lived in the desert, poor familiy, etc). He takes us to a shop which is quite near and asks for some sort of "dried butter" (?) and gets 1kg package. "My family can live 1 day with this". (very touchy, he looks as it is even going to cry). I look at the price, since prices are always written in Indian products (thanks God for us foreigners!) and then I see a hand written price covering the "right one" which says something like 500 rupees (could be more or much less, cannot remember, but really really high in India). At first, I feel confused, stupid, guilty and even selfish, about denying food to a kid, but "13€ is muuuuuch more than back at home!". Hand-written price. No way this trick or scam. (bring the butter back, share the 500 rupees with the tender).

Feeling scammed, I say to him: much better luck with next Spaniard. The, kind soft, friendly Indian kid looks at me as if he wants to kill me, makes a fist each hand and Mr Hyde comes out. Wow...

From then on, I only give my very own biscuits if i feel like... and still have to count how many times beggars (who were asking for food) refused them! As Indian tourism motto: "Incredible India".

Islamic countries, i open muuuuuch more my pocket, since it is a totally different actitude.