If your hair is both fine and thin or thinning (sparse):
Stylists say a short cut best, but how short is too short? This depends largely on your facial shape. If it's round, go with a longer, short cut to slenderize your face. If it's elongated, create the illusion of width with fullness at bottom. If it's diamond-shaped, keep the length below widest part of your face. Of course, there are plenty of times you'll want to break these old rules, which were created to "downplay flaws." If you've got confidence and attitude, you can even look great highlighting a feature that has been traditionally downplayed.
Wear your hair smooth and close to your head, with the ends flipped up or under. Try cuts that were intended to be worn behind your ears. This naturally makes it look like you've got more hair.
Ask your stylist about variations on the Cap, Bowl and Crop cuts. Consider what bangs bring to the table, besides concealing a sparse, irregular front hairline. When the back is cropped super-short and the long front "bang" area is worn close to your head, you can go for a smooth style or add a few layers for texture. Imagine a cut with all the hair from crown brushed forward and cut into heavy bangs. You can trim the sides around your ears, leave wispy sideburns or let bangs continue into a softened bowl cut. A good stylist can blend the best elements of each of these cuts.
An asymmetric style makes it look like you have more hair. The cut stacks up on the heavy side and lighter side is supposed to look like less. Tuck the lighter side behind your ear and all that fullness on heavier side stands out even more.
The cardinal rule is "kept simple." Consider a short cut that does not require much volume, or a longer look that gets its kick from a smooth, shiny surface.
If like a longer look, get trims religiously. Fine hair looks its worst when it starts to lose the shape of the cut and the first sign is straggly, ragged ends.