"rules" for one handed signing?

One handed signing is considered VERY casual. This isn't something you would do in more formal settings. It can be difficult to understand at times, depending on the person and your mental state at the time. There are no rules for it. It's just something that's picked up over time. Think of it like slang English, we just pick it up as we go. And yes, it's just signing hoping people get it... ;)