All the suggestions already mentioned are good, and helpful, I think, if you’re trying to determine how you learn first, and then use that information to better help you to retain information. However, personally, regardless of exactly whether you’re a visual, audio, hands-on, or rote memory learner, I find that teaching yourself as if your knowledge is meant to teach others is the best method. For you will find that if what you learn you can actually share as with others, it will usually mean that you, yourself, have learned something, that is RETAINED something new!
On that note, when attempting to teach yourself something this way or teaching others what you’ve learned, it truly helps if you can find a logical method whereby you can apply your new knowledge accordingly. For instance, in the case of history, if you learn something that happened in the past (ie: is historically accurate) figure out how it is being mirrored now or in the recent past and how that has affected you. This really isn’t that difficult to do, since, if you learn about history, you will find it does repeat itself many times over centuries. That’s actually, to me, anyway what makes it so valuable a knowledge, and interesting as well. So this new knowledge, you can tell yourself you know by way of sharing it with another person. And this can also be simply done, the same way you “taught” yourself; by demonstrating and discussing with the person you’re trying to teach the information to, how such information is relevant to their lives as well.
Hopefully, I’ve not lost you by this point, because in the case of science, it’s even easier. Since science IS a science; or as one definition explains it Science is “any systematic knowledge-base or prescriptive practice that is capable of resulting in a correct prediction, or reliably-predictable type of outcome.” For this reason, Science is something that comes with proof, rather than simple opinion. That means that for the logical mind, this knowledge is tangible and therefore “share“able. Again, as with the history knowledge, Science can be applied to your world as it is right now. So then if you’re following my methods of teaching what you’ve learned, you can share this information by re-applying it to your new pupil’s own life, so it becomes relevant information to you both.
Hopefully, that made sense. Memorising will likely get you through exams, but the proof of your knowledge will only ever then be in your grades. Actually learning the information will allow you to apply it when called upon to do so in your own future… like for a job or promotion.