First you should test to see if they are non-linear If you find them to be non-linear then a series of transformations using roots and powers can be used to make the data more linear. Tukey's ladder is the easiest place to start.

http://onlinestatbook.com/2/transformations/tukey.html

Whatever software you use the process is the same. You create new variables from the Y (most commonly although sometimes you transform X) applying the right power transformation until your relationship is linear. It is essentially a trial and error process - you start with the less extreme transformation and move to the more extreme ones until the relationship is linear.

Note that this process won't always work. Some relationships are inherently non-linear. In some cases this can be addressed, but I don't remember the process (which is complex at best).