How to get more gas milage on a 06 minivan?

My dad drives a 2007 Toyota Sienna, i'm tryin to figure out how to get more gas milage on this van. So far I told my dad to inflate the tires, don't accelerate downhill , and removing unnecessary weight in the car, and removing the bars on the roof rack. Do you guys know anyother ways to improve gas milage on this minivan? Plus i wondered that what if we bought a cuastom suspension to lower the van for more direct airflow does it sound a good idea?