I think that part of the issue here is teaching our children to balance humility with self-esteem. We've been struggling with this at our house. DD is an extremely adept child both physically and intellectually. Adding to that she is the kind of child that people stop on the street to comment on her appearance. blush My dd has generally been walking around like she's on top of the world her entire life. So! With that we have her believing deep down that she is the world's sweetheart and that everybody loves her.
So far, we've been trying to temper that belief by teaching her to search for the positive qualities in everyone else she meets. We talk about her friends and discuss all of the good we see in them. We're hoping that this practice will help her to see that we're all in this together and that no one is better than anyone else.
Having said that, when my dd is complimented we accept the compliment as graciously as possible and change the subject. We wouldn't ever want dd to think that being smart (or pretty or musical) is something to be ashamed of.
Later on I will sometimes ask dd why she thought that the compliment-er said what they did and we'll discuss why they were impressed. If we have the opportunity we will talk about the positive qualities of the compliment-er but if we don't know them well we don't or I'll mention how kind they were to notice dd or to speak such kind words.
We don't spend a lot of time on it but I feel that it is important to acknowledge the compliment both to the speaker and with my dc.