There are two beginner programs you can use (listed below).
If you are proficient with the lasso and working with grads and textures you can do them like that for better results.
For the ones with wacom boards it is much easier and you will get much better results. First you need to use the pen tool and draw out your rip pattern for your base. Some people may want to save it as a brush after you get several done. Others may want to save them as a png-psd file to make it go faster the next time. also in some of the PS programs you can use the rubber band effect with the wacom. Now your expensive wacom board comes with this already built into the tablet itself.
For beginner rip tear style try these CS4 addons:
you will not get great results but it is a start. I would do a tut however I prefer all of you to practice and do it your way. Also, i fail ever time I have tried to do a tut.