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You want lots of volume in your hair. Hey, flat, lifeless hair is nothing but boring. What you don't want is a lot of bulk right at the ends. This can leave you with an disproportionate hairstyle, since you want most of the volume around the top of your head, the crown area and not at the ends. To avoid looking like a triangle, get a cut that removes a lot of that bulk, for the most flattering look.
Pixie Cut
The pixie cut, a la Emma Watson and Carey Mulligan, is a terrific choice if you're trying to thin out your hair at the ends. It is a quite short 'do, closely cropped to the head, tapered around the nape of the neck and slightly longer on top and at the sides. Add some volumizing cream around the top of your hair and tease at the crown when styling to add major oomph to your coif.
Bob
The bob cut has really never lost its popularity and probably never will. There's good reason for that, and it's because the cut is flattering on pretty much all face shapes, as long as it's cut right based on the person's face shape. For the best results, go with an angled bob, which is shorter around the back and longer at the sides. Get the ends cut with a razor, which makes them light and swingy.
Short and Choppy
A short choppy cut is ideal if you're trying to thin out the ends of your hair. You still get major volume in your locks, but the cut reduces bulk at the bottom by sectioning your hair up into choppy layers. Former American Idol finalist Kimberly Caldwell is a perfect example of how chic a short, choppy cut is and how flattering the style can be.
Long Layers
If you're a long-haired lover, you don't have to cut your hair short. You can keep your length as long as you get the right cut. Get longer layers but tell your stylist to make lots of layers on both sides, so the front of your hair is really thinned out but you still have lots of volume around the crown and at the back. Your shortest layers should be framing your face, with layers ascending all the way down to the ends.
Tips
Adding some color into your hair can help further, by creating the illusion of less bulk at the bottom of your hair. Highlight around the top of your hair or go for dip dyed effect by coloring around the top section and the ends of your hair with different colors.

