Use a complex password - not from the dictionary, not your cat's middle name, not your mom's maiden name.
A pretty easy way of doing this, that I was taught, is to use quotes or lyrics you know. Just take the first letter of every word, throw in some numbers that don't have a personal connection to you (decimals from Pi or e for example) and you end up with a password that is easy to remember, yet hard to guess.
Example:
We are all in the gutter, but some of us are looking at the stars - Oscar Wilde
Ends up being: WaaitgBsoual@ts653589
Quote + easily exchangable symbol + 3.141592
653589 = New password
Also a password database is an option where there is an option to automatically generate a complex password.
Software like KeePassX is a good one for that. It let's you securely store your passwords. Database itself is password protected too.