Gmail is one of the most popular email services.
Whether you use it for personal communication, work, or both, you'll get
more out of it if you understand how a few core features work.
This edition of Get Organized, a weekly series, explains a couple of
Gmail's signature features and explains how best to use them to keep
your email account effectively organized so you can be more productive.
Message Threads
As all Gmail users know, a continuous email exchange gets stacked into a
thread. The number of messages in a thread always appears in
parentheses next to the summary of names on the exchange, a thread
count, if you will.
The message thread is one of my favorite features of Gmail because when
six people reply to one single group email, all I see is one unread
thread rather than six unread messages. What I internalize is that there
is a discussion that requires me attention. If I see six unread
messages, I instead get the feeling that six things require my
attention.

When you open a thread, messages that you've already read remain collapsed, while unread messages expand.
Best practice: One of the best tricks in managing threads
is to keep them intact as long as they don't deviate off topic. When
they do change topic, start a new thread simply by changing the subject
line when you reply. You don't have to start a whole new message. All
the recipients will be included in the new thread, and the history of
your communication will still be archived within the message itself,
under the ellipsis that says "show trimmed content" when you hover over
it (see below), so anyone can reference it.
Labels
If there were one single feature that signifies Gmail, it would be
labels. The way to understand labels is to describe what they are not:
folders. Labels in Gmail often look like folders, and to some extent
they achieve the same end. But labels are fundamentally different than
folders, and mistaking them for folders will really limit what you can
do with Gmail.
Let me start by explaining a little bit about folders. Email folders,
often designed in a tree structure with the ability to add sub-folders,
work similar to how real-world folders do. You file things into them.
If you have a message to file, you can only file it into one folder.
Labels in Gmail look an awful lot like folders at first glance. When
you create a new label, it appears on the left rail, similar to where
you'll see folders (with default settings anyway) in Yahoo! Mail,
Hotmail, and Outlook. These Gmail labels can have colors assigned to
them, too, making them look even more like folders.
So what's the difference?
Any given message thread can have more than one label, such as "work,"
"October 2012," and "urgent." Gmail also gives you two labels
automatically: stars and "important," designated by a yellow tag on the
left side of messages that are sent directly to you, i.e., not
listservs, advertisements, or other mass mailing.
Think of labels more like tags. And the visual labels that you see on
the left rail—think of those as a quick button to sort all the messages
that have a certain tag. Note that even your inbox is just a label.
When you click on a label on the left rail, you'll see new text
automatically appear in the search box at the top.
This text is helping to refine your search to only messages with the
label in question. Remember, Google is the company behind Gmail, and
Google that company was founded as a search tool.
Best practice: Use labels in Gmail liberally because
they aren't a substitute for folders, but rather a way to categorize or
tag items and make them more searchable.
Power users should explore the Settings area to configure more
advanced labeling attributes. For example, you can set up rules or
filters to divert certain kinds of mail to a label, and have that label
show up in your left pane only when it contains unread messages.
More on organizing email: