Any Rails code documentation best practices? Yard vs Rdoc?

Main question:
I've been looking into documenting my own code, and came across Yard and Rdoc. Right now, just trying it out, I have Yard installed. But are there other alternatives out there that I should consider and is there a reason I might want to pick Rdoc over Yard?

Side-Question 1:
I've never done documentation for my own code before since I basically stick to the RESTFUL and Rails conventions, so my code has been quite self explanatory. Where things get more complicated, I usually leave some comments (though I generally try to avoid this, because if it's complicated, usually it can be refactored). Is this a bad practice? Should I be documenting the codebase regularly moving forward?

Side-Question 2:
@Chris, any chance you will make a video series or just a single video on documenting Rails code?