I'm going to have to forcefully disagree with #11 - "Write jokes in comments".

When I encounter a jokey comment, I always think "if you had time to think up and write this joke, why didn't you have time to make an efficient/readable/less buggy function here?"

Also, the jokes I've encountered have always seemed dated, stale, and maybe irrelevant.

Please do not do this, ever. Flat, no-nonsense comments, please. Don't inject personality, and you should consider using E-Prime in English-language commentary. Any use of "to be" verbs in comments obscures what you write about.