Meditation, what it is and how to do it is defined and described in many scriptural texts. Meditation is concentration on an object, not necessarily God. Completely emptying your mind is a later meditation which is got by first learning to concentrate on one object. Think of one sattvic object which brings peace to your mind and which you find your ability to concentrate easily on. Perhaps a saint or Incarnation of the Lord, or even a peaceful mountain or scenery. After you learn to concentrate on one object, then your mind can eliminate that object and concentrate with no thoughts.
Patanjali describes the various stages of meditation in his Yoga Aphorisms. Swami Vivekananda gives them with this description (Complete Works, V1 p 137, and V6 p89):
Pratyahara or the restraint of the organs sense from all outward things, and directing them entirely to mental impressions;
Dharana or steadfast concentration;
Dhyana or meditation; and
Samadhi or abstract meditation. It is the highest and last stage of Yoga. Samadhi is the perfect absorption of thought into the Supreme Spirit, where one realizes, "I and my Father are one."
The Bhagavad Gita chapter 6 tells how to do meditation as does Uddhava Gita chapter 9. In his Yoga Aphorisms, Patanjali gives the steps leading to and the various stages of meditation in chapters 1 and 2. Patanjali says chapter I verse 2 (Swami Vivekananda translator):
Yoga is restraining the mind-stuff (Chitta) from taking various forms (Vrittis).
Meditation is turning the mind away from the senses and concentrating it on an object or a series of objects. Swami Nikhilananda in his introduction to his translation of Sankara’s Atmabodha says (pp 100-103):
There are two kinds of meditation, namely, the objective and the subjective. In the objective meditation the Ideal is regarded as outside, and in the subjective meditation, inside, the meditator. The objective meditation is, again, of two kinds, according as the Ideal is associated with or conditioned by a sound-symbol (sabdanubiddha) or by a form-symbol (drisyanubiddha)…
In the subjective meditation the Ideal is placed within oneself. Vedantic seers speak of the heart as an extremely suitable place…
As in the objective meditation, so in the subjective meditation, the Ideal may be associated with or conditioned with by a sound-symbol or a form-symbol.
Meditation as been described as similar to the pouring of oil from one container to another (continuous with no breaks in the flow) or as the steady flame of a candle.
Swami Vivekananda has said (Complete Works V7, p 71):
Control the mind, cut off the senses, then you area Yogi; after that all the rest will come…You continually do it unconsciously as when your mind is absorbed; so you can learn to do it consciously.
Learn to control the mind, turn your mind away from the sensual inputs that are bombarding our minds continuously. Once the mind is controlled and turned away from the senses, you can (as Ramakrishna Paramahamsa said metaphorically speaking) sit back, light a pipe, and just hold the rudder steady to reach the goal.