Free Kicks provide an excellent opportunity to score, but many ignore this and don't learn the proper techniques. Before I got the techniques down, I was enraged when my opponent slide tackled me on a breakaway and I got the free kick, but now it makes no difference because it is just as easy to score free kicks as it is to finish off a breakaway. Read more here.
Penalties are easy, its a given. As it's just guessing, its really a matter of statistics, which favor the kick taker. Obviously though, there are ways to increase your chances of putting it away from the spot, and likewise for saving penalties. Read more here.
Corner Kicks are a mixed bag really, it's hard to call them a consistent scoring opportunity, at least in FIFA 08. Besdides whether you have big, strong players in the box, the only thing you really can control is how you play the ball in, and this tutorial goes over the best methods of doing so. Read more here.