Pruning will become natural once the principles are established. All trees and plants will thrive with pruning though not all require it. Unlike fruit trees berries grow out every year from the ground up. They do not require 'trimming' or 'thinning' cuts. The cuts in general will be all or nothing.
The first and primary point to understand is in regards to fruiting wood. For berries it can grow on New canes, 1st year canes, and even 2nd year canes. This depends on the variety you have selected. There are reasons to have them all and reasons to stay away from them, but it all depends on personal preference. Typically they are distinguished in two ways: Primocane bearing and Fluorocane bearing.
Because these two types are so drastically different you must find out which your are. This can easily be done by contacting the nursery they were purchased from or by researching the variety you 'know' you have. If by chance you have no clue what variety you have and did not plant them yourself there are a few ways to figure it out.
Distinguishing between Primocane and Fluorocane Blackberries: