First you have to read a few spiritual books which explain the various ways to start meditation. Then you start. Soon you will see that reading books is not enough. You will feel that you need a teacher, who will know which kind of meditation will best suit your nature and soul. If you do not have a teacher, pray to God to reveal within you the kind of meditation you should adopt. Then, during a dream or in your silent mood, God will make you feel what you should do. Now you can begin your journey.
When your meditation is correct, you will feel a kind of joy all over your body. But if you do not feel that joy, if, on the contrary, you feel a mental tension or disturbance, then you should know that the kind of meditation you are doing is not meant for you and is not advisable. When you get a feeling of spontaneous inner joy, then the meditation you have adopted is correct.