1v1 verses a keeper should usually be the surest opportunities to score.
The basic idea is you want to dribble the ball toward the keeper, and wait until the moment RIGHT as he charges you, but before he's in range to grab the ball. At this point choose a corner and tap the shoot button - you don't need a lot of power.
It's all about the timing - ideally, the ball is on your foot at the exact moment the keeper charges, so there's no delay from the time it takes to catch up to your dribble. That's why I like to NOT be sprinting when I'm 1v1 vs a keeper - more frequent touches means less time in between dribbles.
So a typical 1v1 would look like this:
-you receive the through ball beating the defender
-sprint toward the keeper
-STOP sprinting inside the box
-wait for the keeper to charge, then AS SOON as he takes that first step
-tap the ball into a corner.
It's something you kind of get a feel for - practice it in the 1v1 mode before the main menu, and you'll see what I'm talking about. Eventually 1v1's will be by far the easiest way to score your goals.