How would I learn to be able to roll my R's?

This question is somewhat related to an earlier question regarding the ability to flutter tongue. Now it seems like I am most likely physically capable of flutter tonguing, but I just don’t know how. I have changed the topic to rolling R’s because it is the same motion, but in a context with which more people are familiar.

This question is relatively simple. I can’t roll R’s to save my life. I am not currently in a situation where it is important to be able to do this, but the whole “I don’t know how to do something I should be capable of” idea has annoyed me / temporarily grabbed my attention. So, how could I go about learning this on my own?

Also, I am unable to roll my tongue into a tube shape (also described as a taco shape) or into a clover. I do not know how relevant these abilities are. These are known to be somewhat genetic. Even though the ability to roll R’s may not be genetic, I do not know how much of an effect a lack of these abilities has on the time it takes to learn to roll my R’s.