Simulate a guided spelling checker
Unlike most other text editors, Google Docs has no formal spelling check process and instead checks your spelling on the fly, as many webmail programs do. If you see a word with a red underline beneath it, you can right-click it to view spelling alternatives.
That technique works, but it isn't as good as a guided program that flags all of your potential spelling mistakes one by one. To make Google Docs guide you through all of your typos and errors, use the keyboard shortcut Ctrl-; to go to the next misspelling in your document and Ctrl-[ to see the previous one.
Claim more real estate
Google Docs wastes valuable screen real estate by surrounding the menu and toolbars with big empty spaces. That extra space, added to your browser's window dressing (called "browser chrome"), leaves you with less usable room to get your work done. To improve this layout disaster, go to View, Compact Controls or press Ctrl-Shift-F from inside a document. This feature reduces the menu-bar size for text documents, drawings, spreadsheets, and presentations.
Keep in mind that you must set this preference for every separate document type. So if you set compact controls in text documents, for instance, your spreadsheets will not use this layout until you also set it in the spreadsheet editor.
If you want even more space, try viewing your documents in full screen. This setting does not expand into your full display size, but it does take over your entire browser tab and hide all of your Google Docs menus and toolbars. Full screen is a good choice for keyboard shortcut users. Setting a document to full screen is not a permanent preference, however; you must enable it every time you open a document.
Turn off notifications
Are you collaborating on an online document, but going nuts due to the constant email notifications from the project? You're not alone. Reacting to user frustrations expressed in several Google Docs discussion threads, Google created a feature that lets you stop email notifications on a per-document basis.
To stop email notifications, open the offending document, click the Comments drop-down menu at the upper right of the screen, and select Notification settings. In the pop-up window, select "Don't send me any email notifications for this doc (not recommended)." If a global opt-out is too extreme for you, several filters are available. You could, for example, choose to be notified only when you are mentioned in a comment, or when someone replies to something you commented on. Once you have the settings you want, click OK.
Open Google Docs in the same tab or window
By default, Google Docs opens each of your documents in a new tab, but you can change its behavior so that it takes up only one tab at a time (for the most part).
Click the settings cog in the upper-right corner of your main Google Docs menu (the screen that lists your files), and select Settings. On the next screen, under the General tab, find the "Where items open" setting (it should be the third item), and select "In the current window." Click Save at the bottom of the menu to exit the screen and return to the main Google Docs page. Your documents will now open in one tab, except when you create a new file or open a document from another document by selecting File, Open.