Hrqls: Grabbing your opponent's 5-point or barpoint is a strong defensive move but escaping is generally better.
That's about it at the start for GS and GG. but throughout the game you'll be thinking about the blot, preferably blots, that you're wanting and you'll be prepared to take greater risks to obtain those blots, unless that strategy become inapplicable.
A prime game is where both sides have a blockade, preferably a 6-prime and each has men trapped. The loser tends to be the one whose blockade crumbles first so timing is very important. If you get big dice and establish a prime but without having escaped your backrunners then find that they're boxed in, you'll also find that your opponent has got midfield blots to soak up a few dice rolls while you have none and must crush your prime.