I especially get annoyed about this at Old Navy. People often come to Old Navy to buy clothes for the various adopt-a-family style charities and they often feel the need, for some reason, to share with me what they're doing.
I was checking someone out a few weeks ago who volunteered out of the blue, "These are for these two girls at an orphanage. I think they'll like them. It'll make their Christmas so much better."
Like, okay, lady. Yeah, it probably will. But why don't you take a step back and stop acting like this is the most important thing ever and, while you're at it, stop bragging. I'm sure she also took a picture of the pile of clothes when she got home and posted it to Facebook so she could bask in all the likes and "You're so generous" comments.
Speaking of Facebook, it's unnecessary to post a status or picture every time you do something nice for someone. It just tells everyone how pleased you are with yourself and how important you think you are.
Of course, sometimes interesting or funny things happen in the midst of doing something charitable, and I certainly don't hold it against you for sharing these things if it's not possible to share the story without talking about the charitable thing you're doing. But you can try to phrase it in a way that makes it clear that you're NOT trying to brag, and that's absolutely not what people do most of the time.
Doing good things for people should be a reward in and of itself. Don't risk looking like a self-obsessed braggart by posting on Facebook about it.