How you know, which Tactic to set?

[Narf]

You're supposed to be the manager, which means that you make the instructions to your players. There's no silver bullet - it's an adaptive game.

How do you set your instructions? I can never get the diamond to work. I'm a fan of it too.

The few times that I've played with a formation that puts a lot of players close to each other in the middle I've used short passes and it seemed to work best in that way - I can tell you that much.

3-4-3 since level 2. Level 6 now. Does alright for me

... and I've never been beaten by a team playing 3-4-3. As I said - there's no silver bullet.