Apparition is a very difficult skill to learn. You must be of age to Apparate, and you must take an Apparition test. It is illegal to Apparate without a licence. The Department of Magical Transportation enforces these rules, and will fine wizards travelling without this licence. When not done properly, Apparition can lead to nasty complications, such as splinching. Many wizards prefer to travel by broom, a slower but safer method.
The sixth year students at Hogwarts are given Apparition lessons by a Ministry Apparition Instructor over twelve weeks, in preparation for their test. It takes place in the Great Hall at Hogwarts.
Wilkie Twycross, the Apparition Instructor, says the most important things to remember when Apparating are the three Ds - Destination, Determination and Deliberation. The first step is to fix your mind firmly upon the desired destination. The second step is to focus your determination to occupy the visualised space - witches and wizards must let their yearning to enter the space flood from their mind to every particle of their body. The third step is to turn on the spot, moving with determination, feeling the way into nothingness.