Shaved Sides with Disconnected Top
For this style, the hair is taken very close on the sides and back with a number one blade. This clippered section is taken up to the point when the head begins to round on the sides. The back ends up clipped to the crown. The top, in turn, is left about four inches long—leaving a distinct and obvious disconnect between the sides and top (e.g. if combed down, the top would hang over the shaved sides). When you style this kind of cut, you're going to want to use a blow dryer to give it height in the front, and some styling product to provide hold and separation.
Classic Pompadour With Disconnected Top
This is a classic men's pompadour, where the hair is clipper cut fairly short (but not totally buzzed) on the sides and back. The hair is blended on the parted side, but left with a definite line of demarcation on the non-parted side. The line of demarcation will disappear when the hair is slicked back, if you opt for that look.
For this style, a classic pomade such as a Murray's, ($6,) is your best bet. Apply roughly a pea-sized amount of pomade to the palm of your hand (too much will look really bad,) and work your hands around a bit to warm it up and emulsify it. Using a brush, slick the hair straight back and slightly to the side. For this one, you might want to use a blow dryer before applying the pomade, to give a bit more height in the front.
Dry Look Pompadour
You might want the aforementioned basic pompadour, but with a bit less blending on the sides and back. Where this style deviates from the classic pomp is that most pompadours are worn with a shiny, wet look while this version is worn dry.
For styling, using a good putty like Fatboy's Perfect Putty ($21) is ideal. When the hair is slightly damp, apply a liberal amount of gel evenly throughout the hair. Comb the hair back and a bit to the side and let it dry naturally. Next, to create the dry look, brush through the hair (which will retain most of its shape from the gel). You might want a bit of hairspray to lock in the style, but it's not necessary.
Pompadour With Exaggerated Length on Top
This is an extreme variation of the pompadour, popular on celebs, in which the hair is cut short and high up the sides and back of the head, and the top is left six or more inches long. In part, it's a basic undercut in that if the top were to be combed down, it would hang over the sides. However, for this look, the top is styled with firm hold gel and the hair is combed up and back, mostly straight with a slight lean to the side. This time, hairspray is necessary to hold the style in place. This style isn't the most versatile due to the extreme length difference between the sides and top—it can only really be worn the way it's depicted.
Brandon Flowers' Haircut
The Killers' frontman Brandon Flowers is shown wearing an aggressive version of the short sides with a disconnected top. The hair is cut high up with a number one blade, and basically not blended with the top at all. It can be styled with a bit of paste (such as Verb's Forming Fiber, $16) to add separation and control. For this variant on the cut, the hair on top is worn a bit more casually and messily, but it can easily be styled neatly combed back, for a more formal look.
Ryan Tedder's Haircut
One Republic lead singer Ryan Tedder has worn a variation of this style for a long time. The hair is clipped short all the way up the sides and back of the head, but not as short as Brandon Flowers's. The top, which is left several inches long, can be worn neatly combed back in a pompadour style or worn down for a more casual look. The back of the hair is neatly tapered, and there's a clean line around the ears. It's a classic barber cut combined with the techniques of modern styling.
Jack Antonoff Haircut
Jack Antonoff, of bands fun. and Bleachers, is the definition of "geek chic" with this unique style. For this cut, his hair is clipper cut short high up sides and back (with the sides and back faded to the skin). The top is left disheveled, allowing his hair's natural texture to do all the work. Donning a pair of geeky glasses adds style to the look. This style is fun and low maintenance. As an alternative, it could be worn slicked back with a bit of pomade for a neater look.