I have heard many people asking about how to cut their own hair in layers, and so I did a bit of investigating, and it appears that it is MUCH much easier than I had expected, provided you don't have terribly thick hair.
I wish I could find the link back to the site that was talking about cutting for a layered look, but my searching is in vain :( Anyhow, here's what you will need: candles, live chicken, chalk, eye of bat, oh, wait, that's for the post on "How to get Microsoft to respond to support requests", not for how to cut your own hair in layers.
Let's see, for this one, you will need a pair of very sharp scissors, not too thick hair, and a few bucks to see a pro in case you don't cut very straight.
Here is how she said to do it:
Wash your hair, and squeeze it dry, don't towel it out, you need it damp and straight, the straight part being most important.
Next, you are going to want to bend over, and comb your hair towards the floor. You want to have the top of your head pointed straight at the floor for this.
Then, after it is all combed straight down, simply take your scissors and cut the straightest line across that you can. It is pretty important that you go very straight, as this cut is the line that people will see from behind when you hair is combed back.
What I read in the forums mentioned that the people there that had used it had had pretty good success cutting their own hair, so long as their hair was not thick. If it is thick, you may still be able to do it, however it may take more than one cut across.
Of course this is a pretty simple hack for cutting in layers, and you may not get it right the first time, but it sounds to me like the theory to it is pretty sound, and if you give it a try, leave a comment here to tell everyone how it worked for you. Please do post your results here if you do this, so I can make any corrections, I am a guy, and I have short hair so I haven't personally tried this one yet. Also, if you were the person who came up with this method, or posted on this method in a forum, please comment so I can give you proper credit.
There is a lot better description of cutting layers correctly in this ebook on how to cut hair. I would suggest you check out that ebook, it does describe the technique better than I can, but if you are looking to save some bucks and forgoe the instructions, then do what I describe above, because it is one way to learn how to cut your own hair in layers.