Summarize this article in one sentence.
Have all of the necessary combs, brushes, clips, razors and scissors nearby. This will save you the trouble of having to reach or look for them while you are trying to cut your hair. Setting them out on a table near where you will be working will significantly help. The better the quality of tools, the better the final product. Hair scissors, specifically, work much better than normal scissors for cutting hair because they are made with sharper blades. Purchase these at local beauty supply stores. Be sure the razor you are using is sharp and fresh. This will make it easier to cut your hair and reduce the likelihood of damaging it in the process. Be careful of cutting yourself. Try to have multiple mirrors so that you can see your head from many different angles. This will help you reach the areas you can't normally see. Position a mirror in front of you, as well as one or two angled toward your side, if you have more than one large mirror. A hand mirror or additional large mirror can be placed behind you in order to view the back. Alternatively, make sure a broom and dustpan are available. A vacuum will pick up the hair great also. Cutting hair is messy. Cover yourself, if you want to, to keep your clothes clean. You can use a bathrobe, a bed sheet, a towel, or any other cover as you see fit. You may also wish to cut your hair in a bathroom or kitchen, which will be easier to clean when you are done. Using a comb, separate your upper layers of hair from your lower layers, around the level of your ears. Tie this hair up and away, so that you can more easily access the lower layers. You may also wish to divide the lower section of hair into three parts: left, right, and back. Large clips can be used to keep the mass of your hair on top of your head and away from the areas you are cutting. This will help ensure that you do not accidentally cut the upper layers while you are working on the lower layers. Using scissors, cut your hair to the intended length of the longest layer. Removing this hair will ensure that you don't waste time layering hair that you don't intend to keep! Start by taking a small section of hair towards the front and comb through to make sure it is smooth, then place and hold it between your pointer and index fingers, to the place you want to cut. It is easiest to start higher, then bring your fingers down to the desired length, keeping the hair smooth. Then cut the section. Take a second section next to the first, as well as a small portion of the cut section, and cut the new section so that it is even with the previous one. Continue cutting your hair until you have removed the excess from the entire layer. Divide your hair again if necessary. Practice on mannequin first if possible! Use your razor to thin and cut your hair. Thinning with this technique will leave the layers of your hair with many different sub-layers. This will help create the "scene" look. Take small sections of your hair and twist this small section into a single strand. Take a razor and run it down the strand of hair, thinning and cutting it. The more you do this, the thinner your hair will be. This not only creates layers but also helps existing layers to blend better. Make sure to go slowly and run the razor several times, to avoid cutting the hair too bluntly or too much. Do not press the razor too hard, you just want to press lightly. Continue twisting and thinning until the lower layers are even along the bottom and at the desired thickness. Thin the next layer of hair to the desired thickness and length. This section should be shorter than the layer below it. Release the upper layers of hair and resection and tie them if you wish to have three or more layers. Continue to thin and cut it in the same manner as the previous layer. Be careful not to accidentally cut the lower layers while working on the upper layers. Continue to a third or fourth layer if you wish to. These layers should be the shortest and also contain less hair than in the previous sections. Make sure you cut all areas and that your hair looks even. Cut anything you may have missed until you are happy with how it looks.This is when having access to multiple mirrors will be most useful.

Summary:
Gather your tools. Set up your mirrors. Cover yourself. Part your hair. Cut excess hair. Thin your hair. Layer the next section. Check for symmetry.