Clocks that run on weights (gravity) need to be mounted high enough for the weights to fall a good distance before hitting the floor. If mounted in this way the clock should run for at least 24 hours before it will need winding again.
For wall clocks, it helps to find a stud to screw the mounting bracket to but not required except for ceiling clocks. It is important to mount the bracket level, so you will need to have a small level.
Full installation instructions will be included with the clock and the minimum mounting height will be written on the mounting bracket.