Dreamwalking Options

It's something I've heard hinted at (in the psi-vampire codex of all places) - the ability to enter other people's dreams.

Does anyone know anything about methods, possible signs of being "dreamwalked" or ways to combat it?

I've actually been able to something similar to it which involved dream influence, on two occasions but the person was a very strong receptive telepath and I and him also had a strong connection, but here goes.

I got myself into a mild trance and wa slaying in bed before I myself would go to sleep, he was presumably asleep at the time and I just kept visualizing the dream I wanted him to have etc. and sending it to him. The next day he told me about the dream. This is really more like dream influencing but it's more useful than just being able to hop into other peoples regular dreams and does involve becoming involved in other dreams so why not.