Though in principle (and of course with practice) one can meditate anywhere including activities such as walking and even on the battlefield, it is good in the beginning to keep a fixed time and place whence one can be free from too many outer disturbances. This regularity builds up an atmosphere favourable to meditation and facilitates the process.
As to posture it is certainly helpful to sit in a posture that is comfortable enough to forget the body yet not one that induces tamas. Lying down in habitually associated with tamas and hence tends to induce sleep which is one of the obstacles to meditation. Sitting comfortably in a chair or simple cross legged posture (सुखासन) is no doubt helpful.
We can identify three main techniques, all of which can be useful at different times. The first of them is to simply step back and observe the thoughts, feelings, impulsion and perception as they rise without reacting or judging them. To this one can add self-offering to the Divine Mother with an aspiration to change it on accord with the Divine Will or to purify, tranquilise and uplift them.
The second way is to take up one idea, say of the Divine Presence in all and let the mind run around it, concentrate upon it till it breaks through the wall of nature and experiences the truth of the idea.
Thirdly, one can concentrate upon the Name and Form of the Divine Mother preferably in the heart (centre of the chest) or in the head centre (crown) or even above the head. One could then offer oneself and all one is to Her for become one with Her Substance and Consciousness and Being.
