The start involves conditioning the body (strength, flexibility, co-ordination, endurance, ...) and the mind (attention, receptivity, calmness, sense of intent, stamina, ...). Otherwise, there is no foundation upon which to build effective technique.
Firstly: Drill: where simple actions (rising kick, front kick, horse riding stance punching) induce patterns of movement into the muscles/nervous system/intent. Drills are pre-defined templates which the student attempts to approximate. By approximating more accurately, the student to get the right basic idea and build the body and movement patterns. The student can't yet critique the technique internally. Thousands of repetitions of well-devised basics are needed.
Secondly: Experimentation: where the student repeats some basic techniques, but is searching for the right feel and the right amount of looseness, exertion, timing, ..., which makes a technique functional for them (ie, going beyond the right shape). Personally, body mechanics starts to make sense and form accomodates to the individual's body. Meditation helps. The best advice for this work is to attempt fast and loose methods first, augment with slow and soft, building up to fast and powerful (but retaining the earlier feeling of looseness, softness and quickness) - being 'well-oiled' and 'well defined'.
Thirdly: Power Generation. This is hard to write as text. It is more easily shown face to face, and needs some physical contact (not violence). The idea that a kick or strike is really about 'hitting the bloody thing, really hard', and that defence is about 'not getting hit bloody hard at all' is important. The mind (intent) has a lot to do with power generation. Drill helps. The body must be conditioned for this kind of training to protect the joints and connective tissue. The conditioning leaves a print on the body for all of life. In a good martial art, this amounts to good health, strength and stamina.
Power generation needs very specific co-ordination of the whole body, especially the joints, in transmitting the power from where it is stored, to where it is dumped (eg, onto an opponent, a heavy bag, a light target, or even the air). Storing is hard to describe unless face to face - a first step can be to push at an immovable object (a tree, or a wall, for example), and observed and develop the feeling of loading in potential energy (a "get set" mode). To use this kind of storing in movement takes a progression of practice from light, smooth, easy movement, to light, fast movement, to full-on. The joints need some conditioning to support this - ie, normal training - but maintaining a feeling of "fullness of Ki at a joint" (not strain), so that no point in the body is weak in a technique. A good teacher is indispensible for this.
One good exercise is sparring without using 'blocking'. The partners agree not to hurt each other, but give each other chances - dodge and exploit! Experiment with deliberate movement to self-advantage, OR for the other's disadvantage. Try it!
Observe. Discern.
Find a good teacher.
Have an open mind - test the claims against reality.
Be humble. Learn by awareness of your own limitations.
Commitment - nothing is for free.
Rest. Over-training is a real problem.
Emotional skill! Don't deny emotions, but don't let them rule. See "animal".