Q:

How can we generate energy by using a planet and its satellite

Like magnet on Moon and coil on Earth , as in motor where magnet revolve around coil ..(Notice that it's an idea behind it; I don't want to cover earth with coil and moon with magnet or vice versa; main thing is how to use natural rotational or magnetic behavior) am I right, or we use Earth's rotation itself.

A:

The moon produces tides.  One can harness water level changes from tides to produce energy.  So: indirectly using moon energy.  I thought that this had been going on for years in places like the Bay of Fundy where there are huge tides.  I was surprised to find this link stating that only recently has there been successful implementation - it is tricky.
http://www.cbc.ca/news/canada/nova-scotia/tidal-power-bay-of-fundy-turbine-electricity-emera-hydro-1.3862227

A:

Yes, you can usually 'steal' power via the magnetic field of a planet.
If your planet has a magnetic field, and the orbiting thing (moon, satellite, spacecraft) has a path that crosses the flux lines of the magnetic field, then one can extract energy via a conductive loop or coil.  

The stronger the magnetic field,
the bigger the loop area (times the number of coils),
the faster the orbital velocity,
the more the orbital axis lines up with the axis of the
planet's magnetic field,

the more power you get.  But note that the energy comes from the orbital kinetic energy of the orbiting body.  So small orbiting satellites should only steal power if they're OK with decaying their orbit (e.g. to re-enter.)  IMHO, far-thinking people should avoid decaying the orbit of a massive satellite, just for some cheap power; that's unlikely to end well for those on the planet.  
On the other hand, as in the story cited below (readable online), one can put in power -- and boost the orbit.  This can be useful, since that boost doesn't use any reaction mass!
Suggested reading:
Tank Farm Dynamo" by David Brin
or if you want the physics, math (and IMHO some good, helpful illustrations:
Physics 8.02 Electricity and Magnetism: StudyGuide
I suspect there's a corner case, with just the right orbit about nonrotating planet with a magnet field (one lined up so as never to cut the flux lines of the field) wouldn't generate any power.  However, nonrotating planets usually don't have much in the way of magnetic fields.    
Under normal geophysics of planets with molten metal cores (like earth), there's usually strong linkage between the planet's rotation, core and field  Except during pole-reversal events, in which case, the field will probably be too weak to get anything useful out of it.

