The basic idea behind regression analysis is to take a set of data and use that data to make predictions. A useful first step is to make a scatter plot to see the rough shape of your data. Then, choose a regression method to find the line of best fit. Which method you choose depends upon the shape the scatter plot reveals (is it a line, a curve, or a parabola?) and what special situations, if any, your data has. The following image shows an overview of regression; See below for links to more detail.
Click on the image to zoom in. For more similar images, download the book Encyclopedia of Statistical Sciences, here.