Worship
Rudrabhishek
Abhishek of the linga with water, milk, and bilva, alongside the Rudram.
When
Often on Monday or in Shravan, and also when a house has a need.
In Rudrabhishek the linga is bathed in order — water, milk, curd, honey, ghee, and bilva leaves — while the Rudram is recited. It is worship of Shiva, not a claim to erase trouble by magic.
In a temple or over a small linga at home, keep the materials clean and modest. Do not send the abhishek water down a drain without thought. Offer it to plants, as your tradition says.
This is a general introduction. Sequence, materials, and timing change with family, region, and shakha. Your priest and your own custom have the last word.