Listening to music...As stupid as that sounds. Listen to minimalistic pieces to learn what they sound like. During my mock revision I listened to Symphony of the New World, a Cor Anglais piece, and then bang-that piece came up!
Know your basic facts, key signatures up to four #s and flats.
Know what style questions come up time and time again for your exam board, e.g. WJEC Q1 is usually something to do with tonality.
Identify where on your mock you went wrong. For an A candidate to get a D it may just be exam technique.