Many users who need to send out a standard reply on a regular basis save a copy to Drafts then try to figure out ways to reuse the draft. While this is not the best method for reusing boiler plate messages, if you choose to do it this way, copy the draft (select it, Ctrl+C, S) then use the copy for the new message. Or select the message and click Forward to begin a new message based on the draft copy.

You could also use Autotext (Quick Parts in 2007/2010) to insert blocks of text. However, its just as easy to create a template and they work well for larger blocks of text.

Use Templates & Custom Forms

To use Templates: Create the message - in Outlook 2003 and older you need to use the Outlook editor or choose Actions, New message using Outlook in order to save as a template.

Save it using the File, Save as menu and select template file type (*.oft). This will default to the template location, usually a folder deep in your file system (in Vista, its C:\Users\user\AppData\Roaming\Microsoft\Templates\) . Change this to My Documents or other location that is easy to find and save.

Open Windows Explorer and locate the template then drag and drop it into a folder in Outlook. You can drop it in Drafts or create a Template folder. I like to use one called .Template - the dot puts it at the top of my folder list so I can find it quickly.

Another option is publishing forms to any folder in Outlook. When you do this, the form is listed on the Actions menu when you are in that folder. To use this method, look on Tools, Forms, Publish this form as and select a folder (in Outlook 2007, show the Developer tab to see Publish.) There are some issues with published forms and unless there is code used in the form (which requires publishing) or you use Exchange's organization forms library, a template is recommended.

AutoText & Quick Parts

Either Autotext or Quick Parts allows you to create a large text block to insert as needed. Insert it by selecting it from the menu, or type the first few letters of the text entry and press enter when it comes up in the screentip.

For more information, see How to Insert Text using Quick Parts

Windows Utilities

If you need this capability in other programs, there are Windows utilities that will work with most programs. These include:
Activewords and TextExpander (for Windows and Mac)

Tools in the Spotlight

Quick Templates

Quick Templates is designed for fast insertion of text templates into Microsoft Outlook mail messages. Use it to enter frequently repeated text fragments, reducing the time you spend on message writing as well as typos or misprints in your messages. With Quick Templates you can create a template list and insert the text from template into a message by a single mouse click or through a hotkey you can set for each template individually.

Tools

ActiveWords	Makes Outlook "hot" in any Windows application, so you can look up contacts, phone contacts, etc. no matter where you're working. Be sure to get the separate Outlook agent.
Email Templates	Exchange/Outlook add-on to create custom replies, forwards, signatures -- inserting any type of boilerplate text into your message. Templates are stored in Outlook or Exchange folders and can contain scripting elements (in VBScript or ET's own script language) to build replies that use information from the incoming message. Various extensions can handle such tasks as mailing list subscriptions. For a rotating quote, download the Rotating Text template. Has some issues with Outlook 2002 -- make sure you get the latest update, disable RTF templates, and don't try to use ET as a custom action in Rules Wizard.
Quick Text Hotkeys	Sperry Software's Quick Text Hotkeys, an Outlook add-in that inserts predefined text into emails, has been upgraded to allow full HTML font capability. Text insertions can now be in any HTML format, or the text can take on the appearance of the currently selected font. In addition, text insertions can now be done by toolbar buttons shown when composing an email (for convenience the function keys are still available). This new version is only for Outlook 2007 and Outlook 2010, both 32-bit and 64-bit.
Template Phrases	Insert frequently-typed phrases into your Outlook messages in a click. See all your templates at a glance organized in a multi-level tree structure and easily find the needed one with quick search. Use various macros, assign shortcuts to most often used templates or add them to Favorites. Have a certain template automatically inserted into all new emails, replies or forwards. Share your templates on a network server and let your colleagues use them. The plugin works with Outlook 2003 - 2010.