Kill a group of regulars with a single order - 0/7
This battle is all about timing as James Barret was talking about. There are 4 angles of approach the British forces will take but 3 places they will stop. That is your best chance to give the order and have the men loose a volley on the opposing side. While it seems simple to begin there, there will be numerous troops advancing the longer the battle goes on. It gets very overwhelming toward the end so be prepared to simply be riding from command to command. Get used to where the circle of influence is for each. The more you can get in a single shot, the better.
If you are after Full Synchronization then you will need to pay attention to a number of things. You want to fire on them just before they fire on you. This is in a small window between when they stop moving and them lowering their guns to fire. Each of the 3 squads you command have their own spot to ensure that in their 2 volleys you will be able to clear out the whole of the troop:
The Bridge Firing Spot:
The Left Bank Firing Spot:
The Right Bank Firing Spot: