The longer an email conversation (or "thread") gets, the harder it becomes to wade through that messy, cluttered explosion of text. That's because normally, when you click Reply, Gmail quotes the entire original email and all subsequent replies. Thankfully, you have an easy workaround: In the sender's message, select the exact text you're replying to--the meat of the message, as it were--and then click Reply. Now, when Gmail creates the reply, it will include only the highlighted text. Translation: a lot less mess.
4. Turn off conversation view
Speaking of messy, some people would argue that Gmail's conversation view (also known as message threading) makes things extremely so, as it groups together messages with the same subject. If you'd rather have your messages spread out, and therefore easier to navigate at a glance, head to Gmail's Settings (under the General tab) and select Conversation view off.
5. Master keyboard shortcuts
Hands off the mouse. You can dramatically accelerate your Gmail operations by learning various keyboard shortcuts: R for reply, Ctrl-K to insert a link, Ctrl-Enter to send, and so on. For a full, pop-up list of available shortcuts, press Shift-? while viewing your Gmail inbox. Google also has a webpage that lists all Gmail shortcuts. And if you're a Chrome user, you can learn shortcuts much faster by installing the KeyRocket for Gmail add-on, which teaches you while you work.
6. Make important messages bubble to the top
Email from work, friends, relatives--important. Email from stores, Facebook, and people you don't know--less important. Gmail's Priority Inbox feature can prioritize your mail so that the important stuff appears at the top, where it's less likely to get lost in the shuffle. To enable the feature, head to Settings, click the Inbox tab, and choose Priority Inbox from the Inbox Type selector. This feature can be a little tricky to wrap your head around, so read Google's Priority Inbox overview if you need help.
7. Restore the old-school buttons
A while back, Gmail replaced most of its buttons--Archive, Delete, Spam, and so on--with icons that some users find cryptic, or at least harder to recognize at a glance. If you'd rather have buttons with text instead of icons, you can restore them: Just go to Settings > General, scroll down to Button Labels, and change the setting to Text.