Actually he has the 4.7L V8 ....but still no rotor, cap or wires as Sandman suggests.
+1 on a clean out of the throttle body. It's really easy and effective. Remove the vacuum hoses, remove the throttle cable, remove the IAC valve and take out 3? bolts. Clean it up & replace.
+1 on tire pressure. Consider an alignment too. They're both good for increasing mileage.
Also clean up your battery terminals to ensure a good connection. These things are so sensitive to inadequate battery voltage/amperage.
Toss in a bottle or 2 of Techron and...
THEN try really hard to keep your RPM down to 2K around town and when accelerating from stop and you'll see the mileage go up some. If you're doing highway miles, you might also consider getting the tranny flash that takes advantage of what is commonly referred to here as 5th gear. It will drop final drive gear RPM by about 350 RPM.
'04 Freedom Edition HO & '04 Overland HO (previous '00 Laredo 4.7)