Welcome Sean.
Do you keep track of your fuel consumption already ?
If not, start a fuel record. Online, on paper, in a spreadsheet ... whatever.
It'll tell you what works, or what doesn't, and what you're saving.
Forget the magnets, electrical power rectifying stuff and other scams ...
Changing the way you drive will have most effect on fuel consumption.
Driving slower helps a lot on aerodynamically inefficient vehicles.
Avoid braking as much as possible, and preferably don't accelerate when you know you'll need to brake soon after.
Not stopping is also very beneficial on heavier vehicles - try keeping it rolling.
Plenty of tips here :
100+ Hypermiling / ecodriving tips & tactics for better mpg - EcoModder.com
Not all are equally realistic.
Go through the list once in a while, pick up some tricks, when these become habits, pick up a few more.
Modifying a vehicle is also an option, but beyond a grille block, air dam and increased tyre pressure, thiscan be rather involved for the benefits.
65+ Vehicle modifications for better fuel economy - EcoModder.com
One of the biggest vehicle mods, is asking yourself if you really need a V8 truck to get about.
Seeing how rare they are in Europe, I'd guess they're not really necessary , but it's a touchy subject in the US
