If he tells you in class to memorize something, memorize it! You don't know when you'll need to apply it. Also, homework is always optional but it does look very similar to the test so it would be in your best interest to study it well and ask questions as soon as possible.

Always do the homework and quiz packets that are given to you during class - although homework is never due and quiz packets are rarely collected (and when they are, they are only checked for completion), these resources will help you a ton on the tests. The majority of your grade are tests, so be sure to always study extra hard for them!!