Two Main Pious Mantras for Bhagwan Shiva are
Shiva Panchakshari - Om Namaha Shivaya
Maha Mrutunjaya Mantra - Om Tryambakam Yajamahe Sugandhim Pushtivardhanam
Urvarukamiva Bandhanat Mrityor Muksheeya Maamritat
Omnipresent, Lord Shiva wanted to demonstrate his power to Lord Vishnu and Lord Brahma, so he appeared as a pillar. Brahma Ji and Vishnu Ji, trying to find ends of the pillar, went upward and downward of the pillar respectively. However, both were unable to find either ends of the pillar and realized that there is someone who is more powerful than them. They started praying and Shiva appeared in body form. That day is celebrated as Maha Shivrathri. Devotees on this day perform Shiva Abhishekam and pray to him with various offerings.
God Shiva married Daksha Prajapathi's daughter Dakshayani (also known as Sati). However Prajapathi did not show much respect towards Shiva. Once Prajapathi performed a Yagna and did not invite Shiva, but his daughter Dakshayani went to the Yagna uninvited. Once she reached her Father's place, she felt insulted and jumped into the Yagna kund and was burnt to ashes. God Shiva became extemely angry and ordered his Shiva Gana to detroy the Yagna.
Later, Shiva went to Himalaya Mountains and began meditation. Saint Narada went to the Himalayas King Himvan and informaed him that among the mountain range, Lord Shiva is meditating. Narada Ji suggested Himvan to marry his daughter to Bhagwan Shiva which would result in his benefit as well as salvation of the entire Universe. Himvan agreed to Narada's suggestion but did not mention this to Parvathi. He rather, asked her to take care of meditating Shiva. In due course, Parvathi started wishing to marry Lord Shiva. To wake up Lord Shiva from deep meditation, Kama Deva used his influence and was successful. Angered by his acts, Shiva burnt Kama Deva to ashes. Kama Deva, since then, only lives in thoughts and has no body.
Later, Sapta Rishi (the seven sages) went to King Himvan and proposed Shiva's marriage to his daughter. Himvan happily arranged the marriage of Shiva and Parvati. They have 2 sons. Their elder son is Lord Ganapathi and their second son is Lord Karthikeya who killed the demon Tarakasur.
Shiva and Parvati always remain together and are considered Father and Mother of the Universe. Brahma is the creator of the Universe, Vishnu is the protector of the Universe and Shiva is the destroyer of the Universe.
Shilananda, a devotee of Shiva, performed a long penance to please Lord Shiva. Shiva happily appeared before him and asked what he wanted. Shilananda said, Lord - I wnat you to sit on me so I can carry you around. To grant his wishes, Shiva transformed Shilananda into Nandi (Bull) and adopted Nandi as his vehicle. Happy with Shilananda, Shiva asked him for one more boon. Shilananda asked Shiva to grant him the privilege of first darshan, even before Rudra gana. Shiva granted him his second wish too. SInce then Nandi is installed in front of Lord Shiva in every Temple.
Ons should not stand behind the Nandi to perform Shiva's darshan. You can stand on either side of Nandi to pray to Lord Shiva as the center location is reserved for Rudra Gana. By praying to Lord Shiva once can avoid unexpected death, snake bite and the hurdles mentioned in ones's horoscope. Fasting on Monday's is the best way to please Lord Shiva. Some People also observe silence on Mondays.