As far as science is concerned, these are the things I've seen studies on:
- Repetition. Learning it over and over again, or doing it over and over again masters the skill. No matter what it is or how passionate you are about it, without repetition you'll forget details. And luckily, a LOT of skills are repetition-based.
- Figuring out the logic behind the thing. They changed the whole common core thing, and everyone is crying about it, but the idea is to re-engineer the way we teach math so that children aren't like "Okay, and I put a floating number here because, stuff, and then I put zeroes here because magic and I get the number." They're teaching how to think about math--that it's all a logical approach. Knowing the backstory to something makes it stick and make more sense.
- Relevance to daily life. I'm super passionate about learning the concepts behind unique Japanese words that just don't exist elsewhere. And then I forget them like 2 seconds after I've read them. Because nothing in my life is Japanese. Especially when learning a language, start with what you say and use the most.. because those things will stick a lot faster and easier when they have an actual daily application. In comparison, you might have been a math whiz in high school, never used a lot of it afterwards, and now you've forgotten all your cool stuff because it isn't relevant anymore. Making something more relevant to you makes it stick.
- Multi-focal approaches. When people say they're auditory learners it means they need to hear it. But that isn't the same as they ONLY need to hear it. Usually, when hearing it, seeing it, copying it, and then doing it on one's own it is soo much more effective than just reading a book on it, or just listening to a lecture.
- Mind maps. People do this all sorts of ways--from simple mnemonics, to charts, picmonics, to serious mind-mapping sherlock-esque style. Memorizing things with mind mapping that creates a surreal, visual experience in one's own head of the object makes it far easier to conjure than it just floating in a void of "I hope I remember this."
- Structured focus. Some people are capable of reading something hours at a time and studying only that. But for most people, 20 minutes of dedicated focus time without any interruption is the studied average. A small reward followed by 20 minutes of studying, rinse and repeat, has been shown to be far more effective.. and that was true for me too. I'd watch a 20 minute show in an hour (5 minutes, then 10 minutes, then 5 minutes), and in between I'd also read on a subject, then hear about the subject, and then draw it and watch movies on it. That rounded out an hour, and then I could move on to the next item on the agenda. It's a slow process, but far more sustainable that way.