If you wish to commence the chanting of any particular Stotra, then on that day you must take a Sankalp [Pledge] and start the Sadhana. Then after that there is no need to take the Sankalp again. A Sankalp is usually taken by taking a couple of teaspoons of water in the palm of your right hand in front of the image or idol of that deity; voice your wish or desire and and then offer the water in your palm to the feet of the deity. In the Sankalp you must also state how many times or for how many days you are going to perform the Sadhana.
If you wish to perform a Mantra Sadhana, then write down that Mantra on a piece of paper; take care that the piece of paper is not spoilt or damaged in any way. Then chant that Mantra slowly in front of the image or idol of that deity 11 times with a feeling that you are taking the Mantra Diksha [Initiation] from that deity and are becoming one with that deity. Then keep the piece of paper in the Pooja Place. Then take the Sankalp in the same way as given above.
if you are a woman, then you can take a gap from the Sadhana for the duration of the monthly periods.
For a lot of Mantras like Vashikaran, Maran ,Yakshini and other Tamas Mantras, the procedure is given in the post itself; if there is no procedure given, then it is to be understood that the taking of Sankalp or Diksha do not apply.
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