Grille block should help quite a bit. Pumping the tires up to max pressure should too.
But the biggest thing will probably be driving style. If you're like most "speed racer" types, you're in the habit of stepping on the gas, out-accelerating the rest of the traffic to try to get a couple extra car lengths ahead at each light, wait until the last moment to brake, etc. All these things are huge wasters of gas. Look ahead to the next light, and if you're going to have to stop at it anyway, start coasting as soon as you figure that out. Let all the other speed racers get the couple car lengths ahead of you. Who cares, right? In fact, there's an actual hypermiling technique known as "rabbit timing", where you let the Ricky Racers all get way ahead of you for the next red light so THEY can trip the signal and get it to change. If you time it right and it works out, you can just cruise on through the light that has just recently turned green, thanks to them and their hot rod driving.
Of course, I don't know you, or whether you actually drive like that or not, but if you happen to, changing that can increase your gas mileage a LOT!
The concept has to do with the brakes. Whenever you brake, you're throwing away momentum that was hard won by burning gas. So try to USE that momentum instead of wasting it - coast up to stops, letting your momentum fight wind and rolling resistance instead of more gas to maintain speed, and then throw it away by using the brakes.
The other related concept is conservation of momentum. I'm not too good at this myself because I hate to step on the brakes, and delay braking too long, but in some cases, braking EARLY can pay off so it takes you longer to get to the red light - - - long enough that it's not red anymore! See, if you can avoid coming to a complete stop, that saves a lot of gas, too. So, slowing down a few mpg early, so you can roll through the light in second gear is better than cruising right up to the intersection, stopping, then having to take off in FIRST gear when it turns green.
But if you can get to treating fuel saving like a game, it can make it fun. Whenever I go out driving, I'm looking for a new "high score" - in mpg. It's a lot like racing, just with a differnt goal.... instead of trying to get there the fastest (the least amount of time spent), you're trying to get there with the least amount of gas spent.
