With a new stallion that will be collected for AI, you might want to train him to a phantom. If so, do it before the breeding season starts. With an older stallion it is just a matter of re-introducing him to his routine. If he is experienced and just new to your farm, try to find out from his previous handlers his idiosyncrasies and routines and try to adjust your management to help him settle into his new surroundings. Some older stallions have quirks, and it's good to know them before the season starts.
Some stallions hate to breed maiden mares.
Some stallions don't like certain color mares or certain size mares. Some don't like the breeding apron put on a mare. Learn as much as you can about your stallion before the season starts, and the season will go much smoother.