Basant Panchami is celebrated on the 5th day (Panchami Tithi) of the bright fortnight (Shukla Paksha) of the Hindu month Magh. From this day, Vasant Ritu (the spring season) begins in India. Saraswati pooja is also performing on this day. The celebration takes place when the Panchami Tithi performed during the first half of the day i.e. the time between sunrises and noon.
If Panchami Tithi begins after the noontime and performs in the first half of the next day then Vasant Panchami is celebrated on the second day. The celebration can only move to the next day in one condition i.e. if Panchami Tithi is not passable in the first half of the first day at any point of time. Otherwise, in all other cases, the celebration will take place on the first day. That is why, sometimes, Basant Panchami also falls on the Chaturthi Tithi as per Panchang.
On this day, Goddess Rati and Lord Kamdev are worshiped in 16 ways (Shodhashopchar Puja) during the first half of this day i.e. the time between sunrises till midday.
Shodshopchar Puja Sankalpa
ॐ विष्णुः विष्णुः विष्णुः, अद्य ब्रह्मणो वयसः परार्धे श्रीश्वेतवाराहकल्पे जम्बूद्वीपे भारतवर्षे,
अमुकनामसंवत्सरे माघशुक्लपञ्चम्याम् अमुकवासरे अमुकगोत्रः अमुकनामाहं सकलपाप - क्षयपूर्वक - श्रुति -
स्मृत्युक्ताखिल - पुण्यफलोपलब्धये सौभाग्य - सुस्वास्थ्यलाभाय अविहित - काम - रति - प्रवृत्तिरोधाय मम
पत्यौ/पत्न्यां आजीवन - नवनवानुरागाय रति - कामदम्पती षोडशोपचारैः पूजयिष्ये।
If husband-wife worships Rati-Kamdev after this Sankalpa in 16 ways (Shodhashopchar), their married life turns into a blessing from all the possible ways.
ॐ वारणे मदनं बाण - पाशांकुशशरासनान्।
धारयन्तं जपारक्तं ध्यायेद्रक्त - विभूषणम्।।
सव्येन पतिमाश्लिष्य वामेनोत्पल - धारिणीम्।
पाणिना रमणांकस्थां रतिं सम्यग् विचिन्तयेत्।।
On this day, at the above given worship period, intellectuals (or people related to learning, art, etc.) worship Saraswati. The pooja becomes even more powerful when worshipers recite Saraswati Stotra along with the other rituals.
Goddess Lakshmi (the Goddess of wealth; also known as Shri) and Lord Vishnu are also worshiped together on this day. Some people worship Goddess Laxmi and Saraswati together as well. Usually, businessmen worship Lakshmi. It is considered highly favorable if businessmen recite Shri Sukta on this day.
Above given Poojas (worships) should be performed in either 5 ways (Panchopchar) or 16 ways (Shodhashopchar).
One thing to be kept in mind is that Panchami Tithi is only considered on the day when it is prevalent between sunrise and noontime.