With any more than 12 players this map becomes too hectic for any degree of coordinated play. Friendly fire becomes a major issue as grenades are often thrown indiscriminately. There are also some level design balance issues, e.g. a strong Axis attack can push gameplay almost entirely to the Allies spawn area.

To be the first team to reach the Frag Limit OR be the highest scoring team when the Time Limit is reached.

Try to stay away from the market stalls as these offer little protection from the overlooking balconies. Because of the claustrophobic nature of the map, smoke can be very effective in concealing movement.
It is fairly easy to push the fight to one end of the map, particularly the Allied spawn area. To prevent this, each team should protect the three access points to deny the opposition the chance to infiltrate. A couple of snipers up on the balconies can also help slow down an advance. Another good spot is the hole in the wall near the ramp which leads up to the Allied balcony area.
Use grenades carefully and only if you are relatively certain it won't result in friendly fire. When clearing snipers from the balconies lob them high.
Try splitting your team into two groups and assign one to attack along one side of the map whilst the other team defends the opposite side.