Commenting

Tricky code should not be commented but rewritten

In general, the use of comments should be minimized by making the code self-documenting by appropriate name choices and an explicit logical structure.

I write "assume the reader is an idiot" comments.  Comments before functions or methods explain how they do what they do, with formatted ASCII graphics if need be, and inline comments are limited to explaining what task the following portion of code performs.
If something really breaks into "wait, what did he just do?!" I also highlight that specifically.