Wouldn't want to write the X-Men, and I suppose the X-Men is the ultimate Marvel comic, and I really wouldn't want to go anywhere near it at all, although on the other had I wouldn't mind having a crack at something like the Punisher.
I wouldn't treat a romantic scene any differently than any other scene. I would really say the biggest preparation was chewing gum and breath mints! For a kissing scene, it's all about the breath mints!