ok...shoting is very very complex, to pull off great shots, you must practice practice...
When close to the goal, or one on one, there are many ways to take the shot, I usually tap the shoot button ever so slightly, so you can hardly see the shot bar...and this puts it under the keeper, I always aim for the far post. Ypu can also lob, hit it hard, high, first post, dribble the keeper, all sorts of things...
Long shots are more difficult, you must use players preffered foot, though players can blast it with the other one too. Depending on the players shooting abilities, you may only need to press the shot meter to about 40%, especially if you have a running start with someone like Lampard, 35% will produce a cracker, and aim for the proper side depending on your positioning and the preffered foot. Spin is applied using d-pad, but spin the ball naturally ie. Right footed players spin the ball left....
If you take a 35% shot with a weaker player, its too slow, but a 60% shot with a good shooter may sail over....or may rip the net, saved by the keeper or go wide....
Practice shots, and learn which player likes which shot...