Imagery is a great skill to develop for any body. What personally helps me is to try and visualise what i’m going to do before i do it, then do the activity, then close my eyes again and re-picture how i did it. This gives me a whole sense of the action and also lets me evaluate myself while using imagery. I definitely agree that doing it before let’s say a free throw can help you hit that free throw better than if you hadn’t pictured it in your head, but even if you do hit it, if you go through the whole motion again, your imagery skills develop because you learn to become more conscious and mindful of your actions and you can really see that as you keep doing this, that your imagery improves faster than if you did it just before hand. A good way to try and see if this works for you, is waking up in the morning and picturing your day and then at night before you go to sleep, just replay the whole day in your head and see how it compares to what you had done in the morning. This is just an experiment i like doing and i hope this can be beneficial to others as well.