Hints On Attacking By Land:

When you attack by land, your sailors land on the beach and become soldiers. If you want as many soldiers as possible, attack using a convoy with 10 Ships of the Line. Each one holds 200, for a total of 2,000 soldiers. The town will have two sets of gates, each one guarded by approximately half of the town's soldiers. You need to destroy one of them. You don't have to kill any defenders, but your soldiers will usually attack them instead of the gates if they're close by. Note that you need 1 musket or cutlass for every soldier you plan to send in. Also, if your soldiers are killed, you lose their weapons. Immediately after your attack, some of the killed defenders will be replaced.

- Brute force
This is the fast but costly method. If you have a lot more soldiers than the town, you don't need good tactics to win. The default split between swordsmen and musketeers, 50/50, works well here. Select all of your soldiers and double-right-click on the nearest gate. Then fast-forward until you win.

- Ambush
A minor tactic that gives you a small advantage. Hide your soldiers in trees close to a gate. Then double-right-click on a gate or on defenders to rush in and attack.

- Hiding in trees
You can hide your musketeers in trees near a gate. They will be able to attack, but they'll take less damaged when they're attacked by defending musketeers.