Most things worth doing take serious, sustained effort. If you want to become an expert violinist, you're going to have to spend a lot of time practicing. If you want to write a good book, there really is no quick-and-dirty way to do it. But sustained effort is hard, and can be difficult to get rolling. Maybe there are some easier gains to be had with simple, local optimizations. Contrary to oft-repeated cached wisdom, not everything worth doing is hard. Some little things you can do are like cheat codes for the real world.
Take habits, for example: your habits are not fixed. My diet got dramatically better once I figured out how to change my own habits, and actually applied that knowledge. The general trick was to figure out a new, stable state to change my habits to, then use willpower for a week or two until I settle into that stable state. In the case of diet, a stable state was one where junk food was replaced with fruit, tea, or having a slightly more substantial meal beforehand so I wouldn't feel hungry for snacks. That's an equilibrium I can live with, long-term, without needing to worry about "falling off the wagon." Once I figured out the pattern -- work out a stable state, and force myself into it over 1-2 weeks -- I was able to improve several habits, permanently. It was amazing. Why didn't anybody tell me about this?
In education, there are similar easy wins. If you're trying to commit a lot of things to memory, there's solid evidence that spaced repetition works. If you're trying to learn from a difficult textbook, reading in multiple overlapping passes is often more time-efficient than reading through linearly. And I've personally witnessed several people academically un-cripple themselves by learning to reflexively look everything up on Wikipedia. None of this stuff is particularly hard. The problem is just that a lot of people don't know about it.
What other easy things have a high marginal return-on-effort? Feel free to include speculative ones, if they're testable.