Vrihaspativar Vrat, or Thursday fasting, is dedicated to Brihaspati, the Guru of Devas. Therefore Thurdsay is also known as Gurubar or Guruvar. Those people who believe in astrology offer pujas and observe a fast dedicated to Birhaspati, or Jupiter, for horoscope related reasons. Lord Vishnu is also worshipped on the day in many regions.
Please note that Thursday, especially in Margashirsh month (November - December) , is dedicated to Goddess Lakshmi in many regions and people observe Lakshmi Vrat and pujas on all Thursdays in the month.
The fast begins on Thursday morning and ends on the next day morning. A single meal is eaten on the day – usually in the afternoon or after puja. People usually eat yellow colored food or food prepared using ghee. In some regions the food is made of Chana Dal.
Yellow color clothes are worn on the day and yellow colored flowers are offered to Brihaspati.
Yellow is the favorite color of Lord Vishnu and Brihaspati.
In the afternoon or before evening puja, people listen to the story of Vrihaspativar fasting, or Vrihaspativar Vrat Katha.
In some regions women worship banana tree or plantain and water it.