I’m using the following xkcd comic to help the teachers at my school with their password selection.
There is also a very useful script, created by Steve Gibson, available to test how long it would take a brute force attack to figure out your password with a computer. While I don’t recommend entering any actual passwords you intend to use into an password strength checker (there aren’t that many websites out there, so an hacker could easily steal the passwords you enter into their "password" checker and try them all over the place, thanks to @drdouggreen for the reminder), this can be an excellent way to experiment with different types of passwords.
I also recommend reading this post I wrote about how to change your password for every service you use, without having to memorize a new password for each of them.
As suggested above, we’ve spent many years training people to use complicated passwords which are actually not all that secure, when instead, you can use a longer, much easier to remember, password that is much more secure.