Train At Least One Level Above Your Competition Level

Alex's Dressage Tips

Always train at least one level above what you're competing at.

If you're competing at prelim, practise a little leg yield and shoulder in at home as it will get him looser and will teach him to carry more weight behind. If you practise canter, then just a few steps of trot and then walk, then that will train him to be a little sharper and better balanced in his transitions down from canter to trot in a test environment. He'll not know what you're going to ask him next so is less likely to anticipate too.
Work on 10-12m circles in trot at home so he'll find keeping balance on a 20m circle far easier. If you're feeling brave, have a go at a couple of steps of rein back too, and this will encourage him to square off better in his halts. 
Remember to use effective half-halts before and after every transition and keep a close eye on his ears as you need to avoid tightening and resisting (ears back) at all times. Keep him through, round, soft and connected with attentive ears (in the middle).