when in the formation screen scroll to bottom where the 1, 2, 3 4 are. Move curosr to one and Click on it and it opens a new screen where you can change the formation (e.g., 433, 442 etc) and the sliders. Raise and lower the slider and there is a dialogue box telling you their effects. You will have to select STANDARD stratety to be able to freely move them as far as yo like - all others are bounded according to the strategy (for example the long ball strategy forces defenders to stay in tight so sliders are not permitted to cross a certain intensity level).
For corners, if using PS3, push the right stick towards the player you want to move and and left stick to move them into position. Once a player is in the desire position use right stick again to choose another. If you are playing online you usually only have time to move one around before the timer forces you to kick.