Great javelin throwers usually remember their proper technique not only thanks to repetition, but also repetition, repetition, more repetition, and some repetition for good measure. Oh, and a lot of repetition too. There is no big secret here, a javelin thrower just needs to practice as much as possible in order to remember their throw execution so well that they perform it subconsciously, and can focus on technique, performance and so on, instead of actively remembering the moves.
A big part of it is muscle memory. You practice and practice and when it is time to compete your body can remember the movements. It’s a link between movement - brain. If you are doing this in club sessions, try to practice several times a week. If you are practicing on your own, try for everyday or every other day. A key to throwing far is to have the various moves practiced so well that you do not have to think about doing them, your body just moves (that muscle memory again). That way you can concentrate on the sequence of moves and allow your body to throw the javelin far.
When we do repeated tasks over and over, the subconscious processes of our brain could run autonomously for most of the time.
If a throwing cue has been performed many many times, most of the competitive throw would be managed by subconscious processes. That means automatic. There is nothing to remember, nothing to recall.
Enjoy practicing the small things
If you're not one of the super talented, that probably means building on hours of perfecting seemingly small things. Obsess over small movements, small parts of the routine. Ideally that won't feel like work, instead giving you a sense of accomplishment that's different but just as satisfying as performing.
In the beginning, you feel like you are getting better and better - until you hit a ceiling. From that point onward it can feel like you're not improving anymore. Don't stop there. Most throwers are still far from even getting close to their maximum potential when they hit that first ceiling. In fact, they keep improving from an external perspective. But at a certain point of training intensity, your awareness for your own body might improve at the same or even at a faster rate than your physical capabilities. All of a sudden you start feeling more and more flaws in your posture, your balance and a multitude of other things. The result: You feel like your throwing is getting worse even though you're actually improving. Keep that in mind and you should be one step closer to becoming an incredible thrower without losing your motivation somewhere along the way.
Never assume you know "enough". Keep learning.