You must learn the art of meditation under an experienced teacher.
Practice meditation regularly and preferably at the same time every day. Choose a time where there is least disturbance.
Sit with your spine straight and erect.
A mantra like AUM, Soham, or a Guru mantra can be used as an object of meditation. Its power lies in its vibrations when uttered verbally or mentally.
Practice for about 8 to 10 minutes initially. You can extend your time later on as per your need and capacity.