Buy an RC car. Preferably electric (battery powered)most people start drifting with a tamiya TT-01 cheap because you will crash and reliable) but nitros can work too just cut extra holes to make sure the engine gets cooled sufficiently. 4WD on-road car is a must.(No buggies, truggies or trucks)
2:- Choose tires. You can get special tires (Yokomo, Hpi, Tamiya, etc., etc.) make your own or wrap your tires in electrical tape.
3:- Go out in an open space.
4:- Drive forwards and build up speed.
5:- Turn sharply and floor the throttle.
6:- Follow through. The car should now be sliding, steer into the slide and use the throttle progressively to control the slide
7:- Power out of the slide.
8:- Practice, Practice, Practice