[INeedCoffee]

It depends on what you mean by "intelligence." Are you looking for an IQ? Trying to learn new skills faster? Learn new facts faster? Think faster? Have better recall for what you've learned? Be able to synthesize new things from information you already know? Being "smart" is complicated, and it can mean a lot of things, but here's what I would say is the most general advice from my own life: 1. If you're looking to improve IQ, the most important thing is practice. IQ is mostly based on reasoning and logic, so things like logic games or puzzles, or trying to look at a problem you're having from a different way from usual are good ways to work on it. 2. If you want to learn new skills faster, it's best to find one skill that can be "used" to help with a number of other skills. Anything related to hand-eye coordination can be picked up faster if that's already a skill that you have. 3. Learning new facts is... tricky, but ironically the best thing you can do to learn them faster is to slow down. Your mind can only hold up a max of seven new pieces of information at once, but that's assuming you have a very good short term memory and strong ability to convert short term to long term. For most people, it's more like 3 or 4. Slowing down how fast you encounter new information can improve your ability to recall it later. 4. Thinking speed, unfortunately, isn't really something you can change, at least not in my experience. Then again, I apparently think fairly quickly as is, so I may not be the best person to ask on that front. 5. Synthesizing information also mostly comes down to practice, but it also requires a level of thinking beneath the surface level (though if you're asking this kind of question, you're probably familiar with that) and analyzing each new piece of information to actively look for connections to what you already know.

Yeah, that was pretty long winded and may not even have been entirely what you were asking, but I hope it's still useful to you.