*. User upper and lower case letters
2. Insert a number or two
*. Use additonal characters that aren't numbers or letters. For example, p@ssword (though don't use THAT as your password -- it's too common)
4. Use words or a short phrase that you can remember.
5. DON'T use the same password at multiple websites, because sooner or later, one of those sites will get hacked
To help with all of the above, use a good password manager. Because of #5, I _personally_ don't like online password managers. Google for "password manager" and you'll find many that are recommended. Then make sure you keep your password file safe, AND MAKE A BACKUP of it occasionally!