Learning to reach your goals, starts with learning to reach in the pool.
Why do it:
Reaching full extension in freestyle is a necessary foundation for swimmers at every level. Learning to create a slippery line to glide through the water, which requires balance, and a sense of flying, will allow you the ability to make decisions later on efficiency or speed.
How to do it:
1 - Swim slow, smooth freestyle, focusing the attention on extending the fingers as far out front as possible.
2 - Focus ONLY on extending the hand as far forward as possible, and not on the pull, finish, or recovery of the stroke.
3 - Feel what part of the hand has the most pressure on it. It should be the relaxed fingers out front, not the palm.
How to do it really well (the fine points):
If you're true to the goal of extension, other parts of your stroke will fall into line. By trying to push the hand forward with a bit of intensity, you'll create a better, more direct pull. Focusing on the pull can lead you to shorten the extension, and start you down a path of instinctual reaction to moving through the water.
When the focus is only on extension, there are other aspects of the stroke that start to come together. Better balance will help you drive the hand forward in a more direct line. You'll also connect the arm to the body rotation, which will ultimately give you a more powerful pull.
Youthful exuberance leads swimmers to focus on fast turnover and the pull. Age and wisdom know that it's better to start with the understanding of a full stroke as early in the learning process as possible, then make adjustments as the swimmer grows older.