If there happens to be more than one airport in the vicinity (unlikely in Ft Wayne, I suppose), you can frequently get better deals by comparing the two.
Be sure to manage your pickup/drop-off times. You'll get a better deal with the weekly rate, but an extra 3 hours on a Monday can absolutely kill you. I've seen $250 for a week, plus an extra $80 for the eighth day because of the four hours.
Spend a fair amount of time comparing rates for all of the possible rental agencies at different times of the day and even different days of the week. There websites will make this easy. Don't just put your first choice into Expedia and see what happens.
Most importantly, scour the web for discount codes. Plenty of people will post their corporate codes and plenty of the agencies offer web only discounts. Rental Car Momma was always a good source of discounts. I've gotten really good corporate discounts, despite not even knowing anything about the business I claimed to be with, but that's slightly risky. Still, RCM will generally provide all kinds of valid promos, and there are a ton of other sites that do the same thing.
Your insurance will cover most events, but also check with your credit card companies. A good Citibank card will also provide some valuable coverage, for example.
Just saw that you're doing a one way rental. Those can really sting. When you're searching every site, look for the itemized price breakdown and see what each one of them charges for the destination fee. One might charge $400 while another charges nothing. Just depends on where they have outlets.
Also, neighborhood shops aren't always the best deal. A lot of the time they're actually more expensive, and you also run the risk of them not having the car you reserve. They tend to be quite flaky about their inventory.
Research is the key. Anytime I travel, I spend weeks exploring flights, cars and hotels. Checking daily for a week or two will give you a great idea of what the trends are and how their pricing works.
Another important thing is having a little flexibility in your plans. It's amazing how things might change by flying out one day earlier or later, same with the return. I'll often base my plans on cheapest travel days and then fill them in accordingly.