Better still – use a password manager KeePass is a good one, and its free. There are variants for Windows, Mac, and Android.
Edited By JasonB on 01/07/2016 09:49:40
Yes, I use it extensively, but be (obviously) aware that if you lose the file it stores them in/the PC dies etc you've lost all your passwords.
One mitigating action is to put the password file into your Dropbox folder (other cloud solutions exist) so it's stored offsite as well – yes, cloud is insecure blah blah blah, but I don't put my really valuable (and mentally remembered) passwords in it anyway.
The other mitigation is to use Keepass for ease-of-use (simple copy-paste of passwords to where you need them) and a black book as the master copy 