At retirement, where should I take withdrawals first: regular IRA or Roth IRA?

Current age is 64, have about $60k in Roth, and $145k in IRA. Am looking to supplement my pension and social security with about $500 per month.
Aside from withdrawing $500 per month I am trying to pay the least amount in taxes and allow the nest egg to grow as long (and large) as possible.