After you acquire data and choose the best econometric model for the question you want to answer, use formulas to produce the estimated output. In some cases, you have to perform these calculations by hand (sorry). However, even if your problem allows you to use econometric software such as STATA to generate results, it's nice to know what the computer is doing.
Here's a look at the most common estimators from an econometric model along with the formulas used to produce them.