How do I kiss my shy boyfriend for the first time?

My boyfriend is very shy. He's already told me that if I don't kiss him, we'll probably never kiss. So, I decided that I would kiss him on o school field trip we're going on. We're going to the movies and then to a skating rink. I figured, "It will be just like a date." But I'm scared myself. It will be my first kiss, and his. You never forget your first kiss; if I mess up, he'll always remember. I really want to kiss him, and he really wants to kiss me. But as I said before, he is very shy, and I am very scared. Should I just do it? Or should I wait for him to kiss me? If I do do it, how?