On Trayodashi/ Pradosham one should invite a pandit and devotely make offerings to Lord Shiva. Those who fast and pray to Lord Shiva on Trayodashi are always healthy and prosperous. Whosoever offers incense, prasad and performs arti to Lord Shiva, with love and devotion, enjoys material happiness and spiritual bliss in this world and hereafter ascends to the abode of Lord Shiva.

"Pandit Trayodashi Ko Lavai Dhyan-Purvak Homa Karavai, Trayodashi Vrat Kare Hamesha Tan Nahin Take Rahe Kalesha
Dhupa Dipa Naivedya Charhavai, Anta Vasa Shivapur Men Pave. Kahai Ayodhya Asha Tumhari Jani Sakal Dukha Harahu Hamari" 
On Trayodashi/ Pradosham one should invite a pandit and devotely make offerings to Lord Shiva. Those who fast and pray to Lord Shiva on Trayodashi are always healthy and prosperous. Whosoever offers incense, prasad and performs arti to Lord Shiva, with love and devotion, enjoys material happiness and spiritual bliss in this world and hereafter ascends to the abode of Lord Shiva.‪ Shiva removes the suffering of all and grants them eternal bliss. Pradosham literally means the removal of sins. This day is an opportunity to remove karma or karmic energies that limit our potential in this current life. Pradosham, which is the thirteenth phase of the dark or bright moon, is the time designated for Lord Shiva to remove the bad karma of people. Pradosham is the worship of Shiva and Parvati when they both are in an extremely propitious mood. There are two Pradosham days in a month. There is only one temple where this daily Pradosham is very effective because of its association with Nandi, the bull of Lord Shiva. The bull was sent to the earth to initiate the daily removal of sins at the temple called Koyampet near Chennai. Participants of the daily karma removal program have an archana ceremony done for them on daily basis during the Pradosham time, ie sunset.
Jai ShivaShakti ~ Jai ShankarParvati ~ Happy Trayodashi!