As I promised above, I will try to explain this bit in as simple a manner as possible, so that you understand the practical application easily. The most important thing you have to remember is that kicking a soccer ball far works on one simple principle, and that is to kick the ball on a spot that will give it the maximum flight. Now it is common sense that if you want something to go up, the force has to come from down. So the area on the ball where you should try to make contact with your foot should be the bottom most part of the ball. To achieve this, you have to get your kicking foot as under the ball as possible. To do this, make sure that when you kick the ball, you tilt your kicking foot slightly so that more of it gets underneath the ball. You should imagine your foot to be like a wedge. The area of the foot to be used is the area in and around the instep. NEVER use your toe. So now you can visualize what is happening. The idea is to DIG OUT the ball, so that it goes up, rather than going straight.
The second important thing to remember is to slightly lean your body back when you are kicking. This enables you to direct the ball upwards.
Do not waste your time in focusing on things like where your non-kicking foot should be placed and how far should your knee bend. This all will come naturally to you.
HOW TO PRACTICE
Knowing how to practice this skill is very important. And it is really not complicated. You just have to understand one principle. And that is to go slowly. The biggest mistake that you can make while practicing is to start off by trying to kick the ball very far. This is a recipe for disaster, and the only reason why many soccer players fail to learn this skill. What you should be focusing on is achieving small distances first. So set small targets initially. For instance, you can set a target of 20 yards, and just try to achieve that till you get the technique right. You will FEEL it when you are able to achieve your target distance by kicking the ball with absolute ease. ONLY THEN increase the target distance. That is all there is to it.