Find out what big numbers feel like. Why is 2^128 so different to 128^2? In mathematics, as in many disciplines, concepts are very important. It's important to develop a feel for numbers.
How to paint a door. There are some special tips how to do this. It's best to do it in the right order and always prepare the surface properly.
In ancient China, craftsmen used skimmed milk and rennet with a little lime to produce a very good water resistant glue. You can do something similar using just skimmed milk and vinegar.