How do I place a call from my original phone number if Google Voice is the default handler?
Not sure if you mean you still want to use GV services, but with your phones' native number? Or do you mean you want to completely circumvent using GV sometimes?

If you meant still use GV, but with your native number:

Voice->Settings->This phone's number

Then just choose your phone's native number (you're still using GV services, but caller-id will show your phone's number, not your GV number).

If you meant completely circumvent GV and use your phone as if GV wasn't installed:

Voice->Settings->Making calls.

choose either Do not use Google Voice to make any calls or Ask every time I make a call