The observance of Somavara Vrata is different from place to place. The couples who want to observe Somavara vrata wake up early from bed and perform spiritual or ceremonial bath. And they start praying the divine couple Parvati Parameshwara (Uma Maheshwara).
The Lord is anointed with Panchamritham (the sanctified mixture of milk, ghee, curd, honey and ocimum leaves) and other sacred substances.
Devotees offer Vibhuthi (Bhasma) and Bilva Patra (Bilva leaves) which are favorites of Lord Shiva. Devotees offer naivedya (food offerings) to the Lord and they perform food charity to their fellow devotees and to the poor.
Legend of Somavara Vrata :
The Moon God observed the Vrata (puja) to get his moonness. As the Moon is also called as Soma, he saluted Lord Uma Maheshwara and prayed to him that this observance be called as Somavara Vrata.
Glory or Benefits of Somvar Vrata:
One who observes Somvar vrata would enjoy every pleasure in the world and after death that person would reach Kailasa (Salvation or Moksha or Shiva lok).