PSA #5 - Appending my gmail's username with +whatever is really handy for me. Whenever I sign up for something new, I'll add that site's name to my email address.
For example, if my email was email@example.com, and I wanted to register with a site called Acme Widgets, I would register with as firstname.lastname@example.org. Any email that site sends me will still show up in my email@example.com inbox, but it will be tagged firstname.lastname@example.org.
Makes it easy to filter stuff, and keep an eye on any site that's trying to sell my email address.