The presiding deity of the first lunar day is Agni and it is good for all types of auspicious and religious ceremonies.
Shukla Pratipad is the name for the 1st Tithi (lunar day) of Shuklapaksha and the 1st day of whole lunar month. It's nature is Vriddhi Prada, which can be interpreted as "rise giver". It's good for following works: marriage; house, entering into a house; Pratishta (fame, honor); shaving; Samskaras like Seemantha, tonsure, Upanayana; peaceful & developmental works; farming; intoxicant & medicine making; oiling; bed; sitting items (Aassan), stone work, cutting of trees, sculpture, Alankar (ornament & decoration works). NB! Some classical sources say that a person must consult astrologer before doing something important from list of actions suitable for Vriddhi Prada Tithi. It's because of the fact that Shukla Pratipad goes right after Krishna Amavasya and because of that Vriddhi Prada works can be performed only during Krishna Pratipad Tithi.