Do create strong passwords with a combination of letters (both uppercase & lower), numbers and symbols.
Do not use easily guessed words for passwords or parts of passwords. This includes family names, birthdates, or phone numbers.
Do use long passwords. As tempting as it is to use the name of your pet, you can greatly increase the difficulty of being hacked by using the first line of your favorite novel.
Do not store your password list in a text file on your computer. Doing so will give anyone with access to your computer the keys to your online universe.
Do use two-factor authentication when its an option.
Do not under any circumstances use the same email & password combination for multiple sites. This goes double for logins to financial institutions and other highly sensitive information.
Finally, do consider using a password manager to organize and safeguard your logins.