A simple and most effective way to learn movement is to follow a very simple three-step process, that is:
I've had very good results teaching people Taijiquan form using this method and it wasn't till I met a neuroscientist that I learnt exactly why this method works so well.
Learning is both a conscious and unconscious process, your conscious mind will learn the movement but so will your unconscious mind and muscle memory. It is when we push both dimensions of our psyche to work that we get the best results.
Every time you learn something, be it a movement or anything else, you create a neural network in your brain. Neurons fire in specific sequences to recall the movement and perform it. The more you practise and repeat, the stronger the neural network gets and the better you remember.
So, when you watch someone demonstrating the movement you start laying the seeds for learning. Watch the demonstration and visualise yourself doing the movement, but do not actually attempt the movement yet. This is important because the brain can only really focus on one thing at any given time. If you try to watch the movement and follow it at the same time your attention is divided and you won't see the movement in sufficient detail. This is why it's so important to watch, and not attempt the demonstration.
When you have seen the demonstration enough times to familiarise yourself with it, then start to follow the demonstrator. At this stage you will start to reinforce those neural pathways you have already constructed in the watch phase. As you follow and repeat the movement, you will start to build it into your muscle memory, so your body will remember, not just your brain.
The Follow phase must last at least five repetitions, because that is the lowest number of reps that is required for the brain to start building a habit. Learning a form is really just like learning a whole new set of habits, only these are movement habits.
Once you have watched and followed, it is time to do the movement. If the movement is new this is the hardest part of the process, as it is hard to recall all of the movement consciously. However, if you remember just the beginning of the movement the rest of your body will kick in and do the rest of it. Your body will have learnt it from the Watch and Follow phases and you won't have to do too much to remember the movement!
It is important to note that if you try too hard to remember, your conscious mind will interfere with your muscle memory and you won't remember a thing. In the Do phase of learning, you must trust yourself to have remembered the movement. Your body will, by this time have it in its memory, those neural pathways have been constructed and it all a matter of reinforcing them.
When you practise, if you hit a block and your mind goes blank, try not to stop completely, continue with the movement even if you do a vague approximation of what you thought the movement to be. Perseverance will pay dividends because your muscle memory will tell you whether you have it right or wrong.
This is because if the movement is correct, it will "feel" correct because your muscles remember even if your conscious mind does not.
So if you can let go of having to remember everything with your conscious mind, the Watch, Follow, Do method of learning movement will serve you well!