u can pretty much tell by how they look...theres no way a human being can spit sumthing from the top of their head and be enjoyin themselves....its human nature to panic and go off flow and keep a strained face under pressure...if there spit is perfect in every aspect except PERSONAL insults towards the opponent, then u know its pre written cos its all great except for the fact that when they wrote it they didnt know who they were battling