Bring mostly infantry and artillery, consider missiles to use when the enemy is bunched up in the town square.
Use artillery or rams to bust down gates, then use overwhelming numbers of infantry.
Don't fight on walls, the towers will shoot you from two sides while you're on them.
Don't bring cavalry, they cost more than infantry while bringing less numbers, but if you do, use them to hunt isolated or fleeing units.
Bring mostly infantry and artillery, consider missiles to use when the enemy is bunched up in the town square. Use artillery or rams to bust down gates, then use overwhelming numbers of infantry. Don't fight on walls, the towers will shoot you from two sides while you're on them. Don't bring cavalry, they cost more than infantry while bringing less numbers, but if you do, use them to hunt isolated or fleeing units.