Windows PowerShell survival guide (Technet)
Checking creds
I’ve encountered a couple of situations where I’ve typed credentials incorrectly into the credentials dialog and immediately use them. Sometimes this causes serious issues; so in order to check credentials before passing them to important operations I just use them to fire-up a desktop application, such as notepad:
Start-Process powershell -Credential $cred -ArgumentList '-noprofile -command &{Start-Process notepad -verb runas}'