Rudra Abhishek is a ritual to please Lord Shiva. Lord Shiva is offered all his favorite things during the process. The Shiv Ling is bathed in ghee, milk, sugar, curd, honey, juices of 5 fruits, Ganga Jal, Gulab Jal, lotus flower, (in special cases, astrologically, one may add one or two things more) while chanting mantras.
Then He is decorated with flowers and offered all His favorite things, e.g. Bel Patra, Bhang, Dhatura, Madaar flower, Sami leaves, etc. followed by Aarti.