Yeah, your best bet is to simply slow down and try not to drive aggressively. I drive 80 miles or more a day and manage about 32 MPGs averaging between 65-70 MPH. I've done my commute at 55 MPH for a whole tank and actually managed 35 MPGs. Your driving style is going to be the biggest factor in the mileage you get, unless there is just something really wrong with your car.
"I do what I can. Sometimes, I do what I can't."