When planning our trips to Kauai, we always reserve our rental cars as soon as we have dates nailed down. I check both Discount Hawaii Car Rental and Costco the I book them cheapest one. After that I continue to rebook and cancel, whenever the price goes down.
For our upcoming trip 10-11-14 to 10-25-14, I first booked last November. We need a full size car this time because we are taking friends and the cheapest at that time was $760 total with all taxes and fees. I just rebooked today for $315 total for the same car and duration.
I canceled and rebooked about six times over that time period and it has dropped over $150 in the last week. I don't expect it to drop much if any more but I'll keep checking. 😄