if he whirls his finger in a circular motion it means your clean to play on after a paint check.
If he's got both his arms in front of his with one going up and the other going down it means u'd been done for a penalty and hes going to do your team for a 1-4-1 at least or worse!
Stay on the good side of refs, take them out for a couple down the local or something... they all still scare the **** out of me... alway think they'll ban me or something whenever one starts walking towards me