What is Power shifting and how is it done?

Power shifting is when you change gears in a manual transmission equipped car at full throttle, without releasing the accelerator (gas) pedal. When you reach your desired shift RPM, you quickly press the clutch, select the next gear and release the clutch pedal as quick as possible without taking your foot off the fun pedal.

Why should one power shift?   

When in a high speed scenario, some people often power shift to keep the RPM up when changing up to the next gear, in an effort to stay in the power band or cut shifting time.

Does it really work?

Sort of - it does provide a slight bump in acceleration and you "land" at a higher RPM, when the next gear is engaged with a slight jerk as you lurch forward. But when in a car with enough power, you will lose traction and just spin the driven wheels, costing precious time and rendering that power shift useless.

Are there any side-effects?

Yes. Power shifting puts extensive stress on the little synchronizer rings that live inside your transmission and the jerking motion will quickly disintegrate the engine mounts, not to mention the loading of unnecessary stress on your entire drivetrain.

Any alternate method to shift without breaking parts?

Yes, definitely. Quick shifting is a much more effective method to get power down without breaking your car or your bank. Just before reaching your vehicle's redline, put a slight amount of pressure on your shifter towards the next desired gear and as soon as you let off the throttle your transmission will let you go into neutral without engaging the clutch. As you pull the shifter towards neutral you have to push the clutch in simultaneously to put it into gear, it will "pop" into the next gear without much effort and you release the clutch as quickly as possible and get back on the gas. All of this should be in one fast motion for an effective quick-shift. When done right, you will shift as fast as you would when power shifting, without damaging your drivetrain. If it grinds, it means you tried to engage it into gear too fast without engaging the clutch fully - this technique is all about practice so don't be scared if you don't get it right the first few times.