Giving to charity is one of the most selfless things you can do. You're giving away your hard-earned money and expecting nothing in return, save the personal satisfaction of making the world just a little bit better. It's easy, too -- literally all you need is whatever cash you can spare and a tiny bit of awareness as to who you're going to give it to.
So by all means, do it. Just please, please avoid messing it all up with one of these mistakes.