Here's a nifty little essay from across the pond…

The logic behind three random words

…on passwords—how to create and manage them to best advantage.

The best advice on the page, IMO, is to use a password manager, the best of which will generate long, random passwords for you after a variety of schemes and remember them, so you don't have to.

You will still need to remember a few passwords yourself, though, so pay attention.