I think your question "how do I remember stuff I don't use often" is not a useful question to answer. Why do you need to remember things you don't use often? Yo

I think your question "how do I remember stuff I don't use often" is not a useful question to answer. Why do you need to remember things you don't use often? You don't. Memory is not binary: you will have easier or harder access to things in your long-term memory. Those that you access more often, get easier. Those that you build up more complex structures around (understanding concepts underlying those concepts) make it easier to retrieve. The more you learn and connect information, and generate it (by writing summaries, applying that information, etc.), the stronger that network of information becomes, which means that when you "forget" it (find it hard to retrieve), a quick skim about that topic will bring the whole network of information back to your conscious awareness. If you want to build better knowledge networks in your brain, you have to (re-)generate that knowledge in different forms. Pick a "node" of that knowledge that's a little fuzzy and learn more about it to clarify it. Draw diagrams of how that knowledge fits together. Ultimately, constant retrieval of information, with restructuring and clarifying, will make it easier to get back when you need it.