What are the signs of a man cheating?

Yeah, I can tell the signs. Like he become extra excited to be alone, or when the phone rings, or closing the door when he sits infront of the pc chatting. Or becomes a little more defensive when you ask him normal questions that you used to ask and tend to give you more lengthy explanations. And doesn't let you used his cellphone, afraid of you finding some personal messages in it.

He takes off after a phone call, he talks about a female a lot, if you ask him if he is sleeping with her he says, "Are you kidding? I wouldn't touch her with a ten foot pole!", if you see him around her, he will be trying to impress her, they make up reasons to be off alone together, (Put itching powder in his back seat and you will know shortly) it depends if it is someone you know or not, the signs can vary. My husband and I have each others passwords on the phone and computer so we can check up on each other anytime we want to, but we don't because we trust each other, but if they are unwilling to share the passwords, that is a good sign.

they suddenly have a new "friend" that they stay out late with, spend more time with than you, yet you've never this "friend". the are more secretive with computer, cell phone, calls, etc. get on the defensive about things quick. Their attitude towards you changes, they become more distant. there's lots of things.