Let's assume your script may or may not need to do a privileged operation, for example write a value to a HKEY_LOCAL_MACHINE branch, depending on some prerequisites. Instead of having to run the entire script with Administrator privileges, you can run only those parts requiring it:
function Start-ElevatedCode { param([ScriptBlock]$Code) Start-Process -FilePath powershell.exe -Verb RunAs -ArgumentList $Code }
This will launch a new elevated PowerShell console, and runs the code you submit. Of course, the user has to click the UAC dialog or submit user credentials to run it.
