To ask this question you must have some idea as to what organization or person or persons you would PREFER to donate to. We know that some charities, for example, have more appeal to a general public than others. Those who market such charities are usually aware of this and each of them endevours to appeal to our 'heart strings,' as much as they can. Guide dogs for the blind, or children with cancer might have more appeal than donating to, say, the homeless.
But why restrict yourself to one particuar outlet. Why not contribute to half-a-dozen, or even a dozen different charities and causes? Donate to one of the bigger, better well known one's and you'll soon be on the 'secret computer list of donors' that every major charitable organization appears to possess. Before you know it, the letters from lots of them will be arriving in your mail box.
It then gets down to discrimmination and preference. You'll need to choose some and reject others or you'll find all of your income is outgo.
For me, I do Plan International (been a member for around 35 years) and half-a-dozen others. I continue to get letters from new groups which I peruse and, as a rule throw into the paper-recycling bin.
Best of luck in your decison and in 2013.