For the first one, Dave has written a nice tutorial on gettimg the tear effect using layer masks. I also wrote one, but mine is more a general description of layer masks and Dave's talks about the tear effect specifically. Check them both out. As for the second, It lookslike you might want to try out the Levels command. Turn the layer you want to get that effect with to grayscale (Shift+Ctrl+U) and then press Ctrl+L to open the Levels dialogue box. Mess with the arrows until you get the effect you want. Hope this helps!