Xcode 4 adds a new "Code Snippets" feature, accessible via View > Utilities > Code Snippet Library. To add a new code snippet, select some text in the editor view and drag it into the snippet library. You can either drag a snippet out and drop it in your code to use it, or, much more conveniently, assign a completion shortcut to it.
When you type in that series of letters, it will automatically show up in the code completion pop-up menu as you type your code. For example, among many others, I have a snippet set up so that typing "svk" will expand to setValue:<#value#> forKey:<#key#>. This can save a lot of typing and/or fishing around in the autocompletion menu for the methods and other code expressions you use the most. Xcode ships with a bunch of built-in snippets that come in very handy as well.
