Vaikunta Ekadasi vrata puja procedure or pooja vidhanam is explained here. Also known as Mukkoti Ekadasi or Swargavathil Ekadasi, Vaikunta Ekadasi is the most preferable day to perform Vishnu Puja.
Dhanurmasam is the great month to worship Sri Hari and Dhanurmasa Shukla Paksha Ekadasi (Vaikuntha Ekadasi) is even more significant.
There is no special rule or regulation to observe Vaikuntha Ekadasi. Similar to other Ekadasi vratham, observing fast (upavasam), Mauna Vratham (remain silent), Hari nama sankirthana, visiting Vishnu temples and Vishnu Puja are the best things to do on this ekadasi.
Vishnu puja with Tulsi leaves (Tulasi dala archana) is highly meritorious ritual to do on Ekadasi vrata. Offer Shodashopachar Puja (16 steps of puja procedure) to Vishnu. Special recipes like Payasam (Kheer) and fruits are offered as Naivedyam.
This is the only day when Lord Vishnu appears along with Goddess Lakshmi hence Lakshmi Narayana Vratham is another auspicious ritual to perform on Vaikunta Ekadasi.
Chanting Narayana Ashtakshari Mantram – “OM NAMO NARAYANAYA”, Vishnu Sahasranama Stotram, Vishnu Purana Parayana, Narayana Kavacham and Sri Ranganatha Ashtakam is highly auspicious.
Here is a sloka to chant on Vaikunta Ekadasi
Sashankha Chakram Sakireeta Kundalam SapeethaVasthram Sarasheery Hekshanam
Sahaara Vaksha sthala Kausthubha Shriyam Namami Vishnu Shirasaa Chaturbhujam