How can I get a better sense of humour?

It’s come to my attention that my sense of humour is lacking. I’ve been told for a lot of my life that I am “too serious”. The one guy I really and truly want to be with even seems to view my sense of humour (or lack of one) as a deal-breaker. It doesn’t match up with his and that makes me sad. So… how can I understand jokes better so they don’t need to be explained to me? And how can I become better at joking around? I mean, it’s fine if he will never be my boyfriend. But I think these are useful social skills to learn anyway. Thanks so much, Fluther!