Find a set of tutorials you like and go through them. Different people learn in different ways, so you'll have to try a few to get the best fit. The same applies to books, if you're into print.
For reference, Autodesk has a Knowledge Base. It's their product, who better to turn to? Nobody can remember every option for every command, and I'm still finding obscure, useful stuff after 25 years.
As always, the best way to learn is to practice. Don't be afraid to make mistakes, you can always bail out of a drawing and start over.