I usually check Expedia/Travelocity for the lowest fares. Then I book an e-ticket by calling CO directly. That way I get the 50% mileage bonus, which is better than the 1000 mile online bonus (in most cases).

By the way, I don't think this 50% mileage bonus for calling CO and getting an e-ticket has anything to do with elite status. I started getting the bonus 2 years ago, before I was elite, and had never been elite. At the time they told me they "randomly selected" onepass members for this promotion. Don't know if I buy that, but I am just happy to still get it.