1. Ok, start off with a new document and fill the background with black. Create a new layer and call it "main lightning". Now, with a 3 width brush, draw random lines like I did below. Then apply an outter glow effect to that layer. Don't overuse it, just a little. I have studied some lightnings so I'm creating this tutorial out of my experience.
2.
Create a new
layer, and call it "lightning branches". Now with
a brush with the width of 2, draw lines going out from the
main lightning.
You may also add some outter glow to this one. Do what you
think look better.
3.
Now create
yet another layer, call this "small branches". With
a brush with the width of 1, flow=50%, draw lines coming out
from the "branches"
(the lightning that comes out from the main lightning) and
lines coming straight out from the main lightning. This gives
viewers thef eeling that the lightning doesn't just end suddenly.
4. Create a new layer, call it "mini branches" and do the same thing as you did in step 3, only here with a flow of 25% and 15%. Like you see in the image below, I created the mini branches coming out from the small branches.
5. Now you are pretty much done with your lightning. You can now create whatever style lightning you want, without having to do filters etc. It is much more realistic, much more you.
More Tutorials: 
