Before a match, ask the ref when the ball is out.

Each referee interprets something different, and when the ball is out is the most common things for this to happen to.

The ball can be out when "a bird can **** on it", it really just depends on a ref.

Regarding scrums and what is a bind and not: Don't ask people, explore it for yourself. You can often bend the rules quite far.  The ref will either warn you, or give you a penalty.  It's worth it so you can see how far you can go.  Do whatever it takes to gain an advantage.