My nerdiness is really gong to show here.
For passwords that I must remember, I use some kind of keyboard pattern, usually alternating holding down the shift key. For example, start with a, and make some kind of shape/trail across the keyboard, holding down and letting go of the shift key every 2 digits for example. Another popular method is creating a few pronounceable syllables, and separating them with hyphens: foj-mip-mong-foog. You could substitute letters with numbers too. Maybe add a question mark or an exclamation point to the end. Really, as long as a dictionary word doesn't appear anywhere in the password, and you have a digit and a special character (preferably breaking up the letters instead of added to the end), it's pretty difficult to crack.
I have no chance of remembering my passwords, though, so I don't try. I have about 270 passwords that I keep track of for websites that I build and websites that I use. They're all between 12-20 characters, but usually closer to 20. They are random letters, numbers, and symbols. I use an application called KeePass to generate, remember, and organize all of them which itself is an encrypted and password protected database. I keep the database file stored in my Google Drive folder, which syncs across the few computers I regularly use, so every time I add a password at one computer, the database is updated on all 4 machines. It's helpful that the database format is supported by password software available for Windows, Mac, Android, and Linux. Probably iOS too.