Meditation is only possible from a state of strong concentration, thus: 

"...concentration is the first and foremost thing a sadhaka or aspirant should acquire in the spiritual path." —Swami Sivananda

Concentration practice is taught in every meditation tradition, yet concentration is not meditation itself; concentration is only the preparation for meditation.

In yoga, concentration is called Dharana, and is the sixth step of Ashtanga Yoga. 

The development of concentration is scientific and methodical, and is possible for anyone to achieve. While developing concentration, one passes through stages:

1. Kshipta: wandering

2. Mudha: forgetful

3. Vikshipta: gathering

4. Ekagrata: one-pointed

5. Nirudha: well-restrained

This lecture provides an explanation of dharana and many practical tips to help you rapidly establish concentration.

"Without wise concentration of thought, the experience of the truth is impossible." —Samael Aun Weor, Spiritual Power of Sound