One important thing to have an idea of - for personal and business reasons - is the amount of inflation expected in the future. Think about it - by having a reasonable number to plan for the erosion of the value of your money, you will better be able to make decisions on what loans to take out, what purchases to make, and how to invest.
Luckily for you, there are a few ways to gauge these predictions, which don't resort to guessing, praying, or going to a fortune teller. The methods are also more sophisticated than taking the last few years worth of data, drawing a trend line, and attempting to extrapolate future results.