(This isn’t worthy of a full post, but we have no micro-hack trick here. I’m hacking Lifehack?)
In Gmail, I keep finding it really useful to hit the Contacts button on the left side navigation area, and then click on a contact’s name. What comes back is a little contact card area up top (complete with picture, if they’re a Gmail user, or if you’ve bothered to add pictures to your contacts).
Below that are all the emails between you and that person. It’s very useful for quickly scanning, and I find it a cleaner, easier-to-mess-with view instead of just applying a filter. (In fact, I’m a bit lazy with the filters).
That is all.