In this game you have to be very reactive to the situation... no one tactic works for every game. Which is just like real life I suppose.
If you're looking for a magic potion of a tactic then you won't find one. You have to build the tactic to your vision and around your team, making changes for different kind of opponents etc.
I recommend going on to Sports Interactive forums and into the tactics section, there is lots of great informative posts which are stickied.
The last thing you'll achieve on Fm these days is instant success. I'd use SI stickies on pairs and combinations and Guidetofootballmanager is also a good site (just google it) to construct a basis for your team. Formation and style, set the tactic into all three slots and train in tactics and/or team cohesion (if new signings ) during pre season.
And for me that's the best advice you'll get, the game will still **** on you though as it's incredibly unrealistic and a quite a lot of the game is incorrectly labelled. Eg - counter.
I've been trying a 4-2-3-1 denmark - I could never get it working on earlier versions and I'm still having issues now. The advice you'll see is often contradictory and it seems everyone as found different ways to work, but I'm the disgruntled section.
Anyway, hope this repetitive advice helps you some.