The existing laws of physics are the foundation for the justification, development and design of a perpetual motion machine. This is an undeniable truth. According to the general opinion, this perpetual motion machine is a kind of mystery in which only the chosen can be dedicated. This is a profound error. A perpetual motion machine is an ordinary technical device capable of converting a certain available energy potential (whether dynamic or static) into dynamic or static energy that is convenient for use. In other words, the perpetuum mobile in general form is an analogue of the turbine in the water flow. Only as a water stream should flow a stream of some other (perhaps still unknown), stable in time, existing where necessary, "energy." The most convenient candidates for suppliers of free energy are "fields" - magnetic, electrical and gravitational:

1. The magnetic field of the planet. Is present in near-Earth space everywhere. Stable in time, but weak in an acceptable scale.
2. Strong magnetic fields of electromagnets and permanent magnets. Mobile and compact, but have a large gradient.
3. Powerful unstable natural electric fields. Occurs sporadically throughout the Earth and in the near-Earth space.
4. Strong electric fields obtained by means of appropriate technical devices. Mobile and compact. Bending.
5. Stable powerful natural gravitational field of the planet. It is present everywhere on Earth and in near-Earth space. At an acceptable scale, a weak gradient.
   The fields specified in points 1 and 3, due to their weakness or instability, are not suitable as convenient sources of "energy". Of the remaining three, the most attractive is the gravitational "field" (Section 5). Artificial electric and magnetic "fields" (items 2 and 4) are promising from the point of view of obtaining minimum weight and dimensions parameters of perpetual motion machines. There is another group of potential sources of "energy": "vacuum", "superconductivity", cavitation and electrovacuum effects, phase boundary states, plasma, etc.
   Particular mention should be made of the weak magnetic field of the planet (1). Its distinctive feature is the uniformity and parallelism of the location of the lines of force. These are very important characteristics, because they, figuratively speaking at first, allow through the magnetic field to "cling" to gravity and prove by their own eyes, the potential possibility of constructing, at least, gravitational perpetual motion machines.
   Ideally, a perpetual motion machine must be powerful, small-sized, wear-resistant, technological, safe, easy to maintain, understandable by design, etc. Putting all these requirements together is difficult enough. Achieving the best result is only a matter of time!