In the Shikshapatri ‘Codes of Conduct’, authored by Supreme Personality Shree Swaminarayan Himself, He instructs His followers about reverence and worship of Lord Shiva:
Slokh 23 - When passing by temples of Lord Shiva and other Deities, one shall bow to them and pay due reverence to the Deities therein.
Slokh 47 - No distinction shall be made between Narayana and Shiva, as they are both proclaimed as Brahmaswarupa (Above all material modes) by the Vedas.
Slokh 79 - They shall devoutly observe the austerities on Ekadashi, Janmashtmi and other birth anniversaries such as Shivaratri etc. and celebrate them with great reverence.
Slokh 84 - My followers shall regard the five Deities named here with reverence - Vishnu, Shiva, Ganapati, Parvati and the Sun.
Slokh 149 - In the month of Shravana, they shall worship Mahadeva with reverence, with Bilva-Patras and the like, or request others to worship Mahadeva on their behalf.
Furthermore, in the First Vachanamrutam of Loya, which are the divine words of the Supreme Personality Himself, He says, ‘I have great respect for Shiva because He has renounced the world, mastered Yoga and a great Devotee of God’.
In the 12th Canto of Shreemad Bhagwatam, Ved Vyas states the following:
…Vaiṣṇavānāḿ yathā Shambhuḥ - Shiva is the greatest of Vaishnavas
Therefore a humble devotee, desiring to please the Supreme Personality should devoutly worship Mahadeva. Devotees desiring to further their faith and reverence unto their Ishtdeva attain blessings from Mahadeva and the other four deities mentioned in Slokh 84 above.
Greatness of Maha-Shivaratri - Shiva Maha Puran
Once a very poor Bhil; Gurudruha was unable to hunt any animal for food to feed his family. He sat down on the bank of a pond and lamented thinking of the consequences his family would face from hunger. He climbed up a bel-leaf (Bilva Patra) tree nearby with the motive of hunting down an animal which may come to quench its thirst.
Coincidentally this was the auspicious day of Shivaratri and he was unaware of a Shivlinga established under that tree. After the first three hours of the night passed, he saw a female deer arriving with her fawns. In getting ready to aim at his prey the sudden movements made some bel-leaves fall on the Shivalinga along with some drops of water from his water vessel. Thus, in this way Gurudruha unwittingly accomplished the worship of Shiva in this time.
Upon hearing the noise made by falling drops of water, the female deer looked up and saw Gurudruha aiming at her with the intention to kill. The female deer pled for mercy and to be allowed to leave her young ones in the safe custody of her stag. She promised to come back. He was initially reluctant but eventually let her go.
Meanwhile the sister of female deer arrived there with her fawns. Upon seeing her he aimed weapon at they prey. His sudden movements again repeated the leaves and water falling onto the Shivlinga. He unwittingly performed worship again as it was the second prahar of the night. Look up to the hunter the deer pled the same and was let free by him as she too promised to return.
When the third prahar began a Stag came in search of his deer and fawns. Upon sighting it, Gurudruhas sudden movements made more leaves and water fall on the Shivlinga hence unwittingly performing worship again. The Stag too pled for freedom so that he could meet his deer and fawns and promised to return to be hunt. He too was given freedom.
Later Gurudruha heard some noises and saw all the three preys coming towards the pond to fulfil their promise. He was extremely pleased at the prospect of getting flesh of three animals. Upon getting ready to aim more leaves and water dropped on the Shivlinga and he yet again unwittingly accomplished the worship to Shiva in the fourth prahar. The thought of hunting and killing no longer remained in his heart. He thanked the animals for their help in his attainment of enlightenment.
Lord Shiva became extremely pleased and appeared before him. He blessed Gurudruha with a boon, that in his next life he would get an opportunity to serve Lord Shree Rama and would gain fame as Nishad. Lord Shiva also told him that by the blessings of Shree Rama he would attain salvation. Whilst describing virtues of observing fast on Shivaratri, Sutji mentioned to the sages, that a fast observed unwittingly on Shivaratri yields such virtues then what could be said about a fast is observed deliberately. The fast of Shivratri bestows both worldly pleasures and salvation.
In the 4th Canto and 59th Chapter of Shreemad Satsangi Jeevan, Lord Swaminarayan elaborate on how to celebrate this festival. Bhagwan should be dressed with brightly coloured garments, and His abhishek should be performed in the evening. Lord Shiva should be worshipped with bel (Bilva) leaves and savoury dishes should be offered to Bhagwan, along with the performance of loving kirtans in his honour.