Procedure of performing the Shiv Ashtakshari Mantra Sadhana is as follows:
1. Start this Mantra Sadhana from a Sharavan month's first Monday or on a Guru Pushya Nakshatra or any auspicious Hindu festive day.
2. Start the Sadhana from Brahma Muhurat.
3. Sit In a separate room where no one can disturb you or enter the room when you are performing the Mantra Sadhana.
4. Sit facing the East and keep a white or red Chowki in front of you.
5. Spread a white cloth on it.
6. Keep a copper plate on it and then keep a Sphatik or Paarad Shivling on it.
7. Do Puja of Dakshinamurthy, then Ganesh, Bhagvati, Vishnu, Surya Dev, Shri Rama and Hanuman.
8. Then Do Puja of the Shivling using Bel Patra, yellow flowers, Chandan paste, rice, black sesame, honey, raw milk, water and Panchamrit. But remember very well that Liquid articles cannot be offered to the Parad Shivling or else you will end up damaging the Shivling.
9. Recite a Kavach and then take a Sankalp for your wishes.
10. Recite this mantra 1 lac times within 16 or 21 days. Do Dashansh Homa with honey and pure Ghee.
Viniyog: || ॐ अस्य श्री शिव अष्टाक्षर मंत्रस्य, वामदेव ऋषि: ,पंक्तिश्छंदः, उमापतिर्देवता, सर्वेष्ट सिद्धये जपे विनियोगः ।।
।। बंधूकसन्निभः देव त्रिनेत्रं चंद्रशेखरं ।
त्रिशूलधारिणं वंदे चारुहासं सुनिर्मलं ।।
कपालधारिणं देव वरदाभय हस्तकं ।
उमया सहितं शंभुं ध्यायेत्सोमेश्वरं सदा ।।
Mantra: ।। ह्रीं ॐ नमः शिवाय ह्रीं ||
Like I have mentioned since last many posts, this mantra too doesn't need Diksha.