Dhāraṇā is a relaxed state of concentration, where you are un-wavered from any distractions. It takes time, it will only occur when the mind is relaxed and present.
The body is completely still, the only movement or awareness of movement is with the single point or object of focus. Most commonly this would be the breath. But it can also be a visual cue like a yantra, the repetition of mantra, or focusing your gaze on a candle flame.
In Patanjali’s 8-fold path of Raja yoga, Dhāraṇā is the 6th limb. It is considered to be the first step to deep meditation.
To achieve this state of concentration you first must physically be comfortable, in a position where you will remain still without discomfort. Gradually withdrawing or tiring the mind of any distractions, a stage referred to as Pratyahara the withdrawal of our senses and thoughts.
Dhāraṇā will happen once the superficial and disruptive surface thoughts pass.
As our spiritual teacher Swami Satyananda says “This state of natural thoughtlessness combined with awareness is a prelude to meditation.”
The actual state of Meditation is a state of being that You may only experience state for a few moments. It is also a process in which you begin to know oneself.