I used to be terrible at accepting compliments, but then one day a friend of mine suggested me to smile and say thanks, even though I didn't really believe they were true (or, at least, I couldn't feel like they were really describing me).
Thinking about it, it was actually the best advice I could receive.
Even if you don't know if the person is mocking you or being really nice, smiling and saying thanks makes you a polite person and doesn't make you look like someone who is attention seeking by saying "no, it's not true, you're wrong, I'm awful" and so on.
Moreover, if someone is making a mock-compliment, this person will not succeed in seeing you embarrassed.Oh, adding a counter-compliment is always a good strategy too (it makes you polite and kind, and it can help shift the focus on the other person if you don't feel comfortable being the centre of the attention).