Do you have any experience barrel racing? If you have experience it helps alot.
You need to train slow pattern work, as well as rating. Before even attempting to walk/trot/canter the cloverleaf, you need to work on spirals, figure 8's, serpentines, and rollbacks. Once your horse can really arch when he turns, then move on to walking the pattern.
Don't push your horse, because if you push your horse to just running the pattern he will eventually become sour and you will have problems in the longrun.