Normally, thoughts are flowing through our mind every second, and it is not possible to stay at one point for any length of time, not to speak of remaining without any thought. Therefore, the first step in meditation is concentration. In concentration we learn to direct all our attention onto one particular point and to forget everything else.
Meditation exercises are the second step. While we fix our attention on something very small while we concentrate, in meditation we start with something small and then we expand into all directions. Often certain imaginations and pictures are used for meditation exercises.
In Mantra-meditation we repeat certain syllables again and again, until the vibration of the mantra, its deeper meaning comes slowly to the fore.
Apart from such exercises there are many little things that help if we do them right: What we eat has an influence, how we dress, where and with whom we meditate, what we do before and after meditation, what music we listen to and so on.