Before adjusting the brake, make sure it is really necessary. One of the reasons of "false" may need to be resultando mount brakes. Check attachment and tighten, if necessary. It is likely that this will be enough.
If the mount brakes everything is in order, experiment with the States of the regulators on the brake handles. If you have nothing positive from these actions is not achieved, check the condition of the brake pads, maybe they have serious defects, then the best option would be replacement.
So, if the brake pads are fine and the mount is stable and reliable, install the regulators on the handles and flip the bike.
Spin the wheel and watch the disc if you have disc brakes. If you noticed that the drive shows any irregularities, or wheel forms a figure eight, the disk most likely, somewhere something hurts. Find this place and correct.
After that, take an Allen wrench and adjust the brake pads relative to the disc. The best option would be, if you will adjust the position to the gap of 1 mm between the pads and disc. Then re-roll the wheel and make sure that pads do not touch the disc when the brake is released, and when pressed they have to touch only the disk. If a little they touch the tires, this is unacceptable.
Spin the wheel as much as possible and sharply tap the brake handle in order to check the sensitivity of the brakes.
If you have rim brakes, and the pads touch the tire, Unscrew the hexagon mount of the cable, the hand holding it, then pull the cable and lock the mount and tighten. To complete adjustment tighten up the Adjusters on the brake handles.