I agree on taking out the seats, spare, etc...
I took out the spare and, of course, all the junk in my trunk.
But one thing I won't agree on is having one gallon in the tank.
I have noticed on numerous occassions that decrease in overall power when I am running out of gas. My friend explained that this is due to a lack of pressure on the fuel pump.
I went with a 1/4 tank (4.25 gallons), but I may try to go down a little more next time.