I would get out my pen and start writing Executive Orders. The first would rescind Obama-care.
I would invite Dave Ramsey and Herman Cain to the White House (after firing half of the staff) on Day 2, and we would spend the rest of the week hashing out a sound financial plan.
I would spend the rest of the month firing bureaucrats, consolidating the Executive Branch, and implementing the plan outlined in step 2.
I'm sure there would be more, but this would do for starters.