There is no single way to meditate correctly and thus this question is quite difficult to answer. Most forms of meditation focus on quietening the mind by focusing one's attention on something else such as the breath, a visualization, the body, a movement or simply the present moment.
Generally, if you are able to sit (or lie) quietly without getting lost in your thoughts or worries and if you feel calmer, happier or more at peace when you have finished, you are meditating well.
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