You should be able to milk significantly more mileage out of that car.. I'm hoping it's a manual
There is a wealth of information in the 100+ driving tips... but I can tell you right now the #1 thing you could do. If you are anything like I was before I started hypermiling, I loved that low-level torque that that light little miata undoubtedly has - I used to have a subaru impreza, and that thing took off. Stop that. You don't necessarily have to start accelerating slower(you'll have to eventually), but I found the best way to save gas was to shift at the LOWEST possible RPM your car can handle without rattling itself to death (stalling). I shift at about 1800rpms, but start off doing it at 2000 maybe... it takes a little skill to walk that line. Hopefully doing this if you don't already will significantly improve your mileage. Oh, and try going the speed limit on the highway. I was surprised at how better my mileage got when I actually obeyed the speed limit (now I go 55-60 on highways even)
Welcome