I agree with most of these, just a caveat on the AC vs windows down. There has been research, and it goes both ways. Essentially, rolling the windows down increases the air resistance on your car, reducing your gas mileage. The question being, does the AC use more gas, or the air resistance from rolling down the windows.
Mythbusters did a segment driving an SUV at 55mph around a race track, and found the AC witht he windows up was more efficient than rolling down the windows: 
But mythbusters then did another test (with more flawed testing standards in my opinion) and found the opposite result, with the windows being rolled down the better option: 
GM and SAE also did a test (in 2004, AC could be more efficient by now, and cars could be more streamlined to have less resistance with the windows open) finding that rolling down the windows was more efficient at all tested speeds: http://www.businessinsider.com/car-fuel-efficiency-ac-air-conditioner-on-windows-down-open-2013-9
At the end of the day, it seems this point is still in contention, and it would require a large, well done test to give an accurate answer.
RE: How To Get Better Gas Mileage, Contributed by @sharingeverybite