Here is a great xkcd comic about strong passwords. I have tended to go for the longer, random passwords which I store in LastPass. I usually pick 20 random characters with text, numbers and special characters. I then update them now and then to keep things interesting.
If I understand this comic, it looks like I may be safer with a couple random words instead. Or, a couple random words with mixed characters within them!
Remembering strong passwords is challenging because they need to be considerably more complex than “1234” (if you are using that as your password, you really need to change it). Like I said earlier, I use LastPass to manage my passwords.
There are other options if LastPass isn’t for you and you should investigate if you aren’t already using a password manager. I don’t know how people manage multiple passwords securely without a password manager these days.