
In my experience the AI tries to exploit the flanks frequently, so the side defenders can sometimes end up with the ball. Control is useful to the sidebacks to hold the ball. Sweeper comes first, so if one player has the highest control and defence skills too, then he should play as a sweeper. In a 4 defenders formation with a sweeper, the sweeper should have the highest defence skill and the two backs on the sides should have the highest controls. Defence can help you get the ball from the attackers and control helps you to hold the ball if you don't have enough action point to pass it forward.
Defenders: You should look for players with high defence skill and as secondary skill control. Goalkeeper: He should have high defence skill, that's all. Later your players will develop and the ball transition could be done with fewer players in the center of the field. You need the 4-3-3 when your midfielders aren't good enough to link the defenders with the strikers. The sweeper will always aid to counter every attack and can balance the missing defenders from the 5-2-3 formation. The defenders should be so organized, that you have 3 defenders in the higher line in the center and a sweeper in front of the goalkeeper also in the center. The strikers should be placed as before, so should the midfield look like too. In the beginning you won't have the requiered quality to pull off a two midfielder line-up, so I suggest to use the 4-3-3 formations in the Amatuer League instead. The two midfielders can be placed as you like or countered the opponents tactics. The three strikers should be placed also in the highest possible row, one in the center and other two next to him from each side with one empty square spaced. The best formation is a flat 5-2-3, where the defenders are in a row in the higher possible line. You have to have at least 4 defenders and exactly 3 strikers. You can try out many different formations, but in the end you have to have some basic rules about the tactics. Tactics: The most important is the tactics.
With vital game engine changes in the future whole tips can be void!) (First of all, these experiences are applieable only in the bottom two leagues and in the current version 0.1.