Why/How should I bed in disc brake pads?
Bedding in brakes removes any glaze from your new pads, and any contamination from your disc rotors. It also transfers material from the pads onto the rotors, which helps them work together. It's essential to get the optimum performance from your brakes when you change pads. Follow these steps:


Clean your rotors - you don't want them to transfer any grease and
grime to your new pads. You can buy dedicated brake cleaner.
Fit the new pads and find a place where you can build up a bit of speed. A hill is helpful for this.
Build up some speed and then brake to a gradual halt. Repeat a few times.


That's probably all you need to do. However some people, myself included, like to pour water  over the hot brakes. I'm not sure this actually improves anything but even if it doesn't it sizzles and steams, which is pretty cool