Improving MPG

Let's start with "what do you have now?"

What do you have and what are you starting with? Just how bad IS the mileage. And how pray tell are you figuring the mileage? ( I used to know a guy who said "I used a half a tank." He meant HE LOOKED AT THE GAUGE)

Have you run a compression / leakdown? That is what shape is the engine in? What kind of miles is on this engine? Use oil? Does it run up to proper operating temp?

How about tune?

Have you checked the "usual suspects" as in does the mechanical / vacuum advance work properly, and while were are there, where is the timing set?

Are you sure the choke is opening quickly and all the way?

Have you done a cursory check to see the carb is not "dropping fuel" into the engine?