Maybe I am paranoid, but I always put one reservation on hold (typically the award reservation), then proceed to book the non-award ticket (provided the fare has not increased). Once the non-award ticket has been booked, then I go back and finish the booking of the award ticket.
If I am booking an award ticket for a minor child, then I have to do the reverse (put the non-award ticket on hold) then call in to have the reservation for the minor booked as an award ticket.