I wonder what are the best or new strategies that you apply in your games? I am not talking about tactics.
Two examples:
In my Germanian campaign I rushed through Gaul and took the Gaulish towns in Northern Italy. Then I saw the Brutii attacking Dacia (allied with me) with big armies and coming close to my homeland. All my armies were somewhere else. My strategy was to
1. block all the bridges across the river that is between Dacia and Germania.
2. Send a small expedition force (high mobile) to Dacia. Brutii were busy chasing them and so they were not able to conquer the Dacian cities.
3. Take the army in Italy and attack the Brutii in Segestica. This cut the supply of their army in Dacia.
After this their army was isolated and immobile. I could easily attack it when I thought the conditions were good.

Another one from the Greek campaign. This is a quite obvious one.
Sicily: You have two enemies here. Both only concentrate on Sicily while you are busy everywhere. So I attacked the Romans and took Messana the very first turn. So they were out of the game. However my army was now split in two and Carthago attacked me in Syracuse. My strategy was not to attack the enemy army that was much stronger than me but to send my Messana troops to Lilybaeum. That made then withdraw their troops from Syracuse. The town was secured and I had time to built up a new army.