Templates and Snippets are a really powerful yet underutilized feature of SSMS. To use templates, open the Template Browser by going to View->Template Explorer. From the browser, you can select the template you want to use by double clicking it. This will open a new query and populate it with the contents of the template. If the template uses any parameters (within angle brackets), you can fill those by going to Query->Specify Values for Template Parameters.
Snippets are used within an existing query window. To insert a snippet, right click inside the editor and click on “Insert Snippet”. Once you select the snippet, you can use the TAB key to cycle through the parameters and fill their values. You can also use the “Surround With” snippets to surround a selected block of code with the If, While or Begin blocks.