Spinning is the natural state of all objects in the Universe. It's very rare that an astrophysical body is not spinning. In the case of the Earth (and planets) which formed out of a big cloud of gas, the spin is controlled by the amount of rotation of the original cloud, but in a not so obvious way. As a rotating cloud condenses it gets hotter and spins faster. It's a basic law of physics to maintain the same momentum, if no outside forces are acting which was the case. But now it's called angular momentum, since it's motion of gas (and some dust, it turns out) is more-or-less along circles and not along straight lines. So all that was needed was a big cloud of gas and dust spinning somewhat slowly to give a small fast spinning planet after gravitational condensing. Notice that the planets are nearly spherical in shape, including Earth. Well, as the parts of the big cloud condense and heat up they go into a molten state, making it easy for the internal gravitational forces acting uniformly in each (in a spherical sense) to make a lot of spinning spheres. In physics we say it's a minimum energy state, which nature always strives for.

Summary of what was needed:

* particles (gas and dust)

* slow spinning to start with; it would be hard not to have some spinning

* gravity to pull the parts together - in lots of places for many planets

* ability to heat up when parts come together

Result: small spinning spheres, called planets (only "small" compared to the big original gas cloud). Notice also that the planets, to a good approximation, have spin-axes all pointing along the same direction. We then have good reason to believe that that direction is the same as the original spin axis of the original spinning gas and dust cloud. We should point out the exceptional planet to this fact is Uranus, which has its spin axis lying almost in its orbit plane, which is almost the ecliptic plane (Earth's orbit plane). We believe that Uranus must have been seriously disrupted by a collision to have put its axis in such an unexpected place. We don't know what else could have done it.