Drive only downhill, in Neutral.
Cold air makes a miniscule difference, if any. The best mpg improvement vs. dollar spent are #1) exhaust from Gibson or somebody and #2) an Xcal2 tuner.
The mpg tip I've found is to just slow down. If I keep it to 70 or less I do a lot better. 75+ and the needle drops like a rock. City mpg sucks no matter what.