Sleep 
When you are awake, your brain creates toxins
Sleeping allows your brain cells to shrink, allowing the toxins to be washed out
While you are sleeping, your brain tidies up ideas and concepts you're thinking about and learning, and strengthens ideas you need or want to remember
If you stop right after sleeping for the night, or taking a nap, you have an increased chance of dreaming about it
You can also attempt to set it in mind that you want to dream about this it will improve your chances of dreaming about it even further
Dreaming helps use diffuse learning to reinforce concepts you are learning about