I, as a striker, can tell you that it comes as a natural when deciding how to shoot the ball. It's something that you don't spend much time thinking about on the field and there's no certain formula for success. Like, you never think about it this way... "if I'm within this range I'll shoot with my inside of the foot, if I'm here, I'll use the outside and so on." It just happens... and it's different for every situation. All you need to do is follow you instincts and know your capabilities! For example, don't shoot the ball with the outside of you foot from 25 meters if you know you can do a max of 10-15 meters of an effective shot.
Hmm, when I think about it though, I think there is a way to kinda "shape those instincts". You need to practice a lot of different positions with the ball. Also, know what you can EXPECT from a certain shot - how the ball curves, where does it go, what's its travel path and so on.. you need to know how strong each of your shots are.
I think the decision on what type of shot to use at a given moment is dictated very much by the position YOU ARE with the ball and the position of the opposing player(s)... defense, keeper and so on.
For the keeper especially, it's important where they stand according to their goal.. if you are atacking the goal from the left and the keeper is covering the near post you might wanna use the outside of you left foot (if you are lefty) or the inside of you right to curve the ball into the opposite corner (far post). But... you know.. it's kinda hard to explain.. it's something that comes as natural once you know on what types of shots you can rely on and given the situation you find yourself in.
keep practicing different types of shots but try to move around... like real game situations.. those will help you a lot.. try to find you limits.. that way you'll know what you capabilities are and you'll be able to focus on how to improve yourselft (... also you won't look like a fool when you try a 40m lob shot at the goalie and find out that you're only able to keep it in the air for 20m...)
real game situations... try different types of shots from variety of positions... both near and far... if you can find someone to be a goalie - even better!
and don't forget to have fun! hope this helps.