Virgins + performance anxiety is like alcohol + bad decisions. They don't always go together, but... Anyway, I generally talk with them for a long time, give them a backrub to make them less jumpy about being touched, kiss for a long time, etc.. If things just aren't happening, I do more backrubs, suggest they play with me for awhile (it's relatively easy to get me off and it boosts their confidence to know that I'm having fun), that kind of thing.
You can just say "I'm not used to this, please take things slowly." We get much weirder requests, I promise!