I bought a truck yesterday and know it will take some time to understand what kind of MPG's it will get, Am I correct in thinking this?

Just after having the truck for 1 day, it gets roughly 16 MPGs as of the 2nd tank of gas. Are there ways to gain MPG's (Better fuel economy from these trucks). Im not looking for 10-15 MPG's more rather than 3-4 possibly 5 more.

Who has done what to their Truck to get better MPG's?

Chips, Programmers, ect.....