ITY ASASYA PRABHOR AGRE GRAHANIYAN NIYAMAM VRATI
CATURMASESU KARTAVYAM KRSNA BHAKTI VIVRDDHAYE
(HARI BHAKTI VILASA 15/113 from NAVA-PRASNA PANCARATRA)
After properly praying to the Supreme Lord near Him, one should properly take a vow to follow the proper rules and regulations and process of Caturmasya to increase one's devotion to Lord Sri Krsna.
EKA DASYANTU GRAHANIYAT SANKRANTAU KARKATASYA TU
ASADHYAM VA NARO BHAKTYA CATUR-MASYO DITAM VRATAM
(HARI BHAKTI VILASA 15/114, Sanat Kumara speaks)
In the month of Asadha, either on the Ekadasi when the Lord sleeps or in Cancer Sankranti day or a full moon day, it is the duty of a fasting person to take a vow to fast in Caturmasya with devotion, in front of the Lord.
YO VINA NIYAMAM MARTYO VRATAM VA JAPYAM EVA VA
CATURMASYAM NAYEN MURKHO JIVANN API MRTO HI SAH
(HARI BHAKTI VILASA 15/116 from BHAVISYA PURANA)
Any person in this material world who performs Caturmasya without following any rules and regulations, or fasts, or without chanting any japa, such a foolish person is considered to be dead, even though alive.
SRAVANE VARJAYET SAKAM DADHI BHADRA PADE TATHA
DUGDHAM ASVAYUJE MASI KARTIKE CA AMISAM TYAJET
(HARI BHAKTI VILASA 15/117 from SKANDA PURANA, NAGARA KHANDA)
(While following Caturmasya) one should give up eating leafy vegetables in the month of Sravana (July-August). In the month of Bhadrapada (August-September), one should give up yogurt. In the month of Asvina (September-October) one should give up milk and in the month of Karttika (October-November), one should give up eating white dahl.
The Chaturmasya Vrata from Haribhakti Vilasa
Bhavisya Purana- "One who passes the Chaturmasya
season without observing religious vows, austerities and chanting of japa,
such a fool although living should be considered to be a dead man."
Kanda Purana, Nagava Khunda- "In the month of shravana (July, August) one should refrain from eating spinach. In the month of Bhadra (August, September) of yogert in Ashvina (September, October) milk. In Kartik (October, November) meat and urd dall.
Various vows and austerities during Chaturmasya and Their respective results.
"O King, one who is My devotee and is fixed in vow, whether man or woman, for the purpose of Dharma, should accept these various austerities and observances. I shall now describe to you all of them along with their respective results.
1) No salt—One's voice becomes sweet.
2) No oil—One's life is prolonged and gets progeny.
3) No oil massages—One's body becomes beautiful.
4) No cooking with oil—One's enemies are vanished.
5) No licorice and oil—One becomes wealthy.
6) Give up wearing unoffered flowers—One becomes a Vidyadhara in Devapura.
7) Give up six kinds of tastes (spice, sour, bitter, sweet, salty and harsh)—One never becomes ugly, smelly, or obtains a bad birth.
8) Practice of yoga—One goes to Brahmaloka.
9) No betal nuts—One becomes happy.
10) No cooked food (raw fruits & Vegetables)—One obtains purity.
11) No honey—One becomes lustrous.
12) No yogert or milk—One attains Goloka.
13) No cooking with earthen pots—One gets ... (?)
14) No hot food—One gets offspring with a long life.
15) Take rest on the ground or on stone—One becomes an associate of Vishnu.
16) One who gives up meat & honey is a yogi and muni.
17) No intoxicating liquors—One becomes powerful and free from disease.
18) Fast for one day—One is honored in Brahmaloka.
19) No cutting of hair and nails—One gets the benefit of taking bath daily in Ganges.
20) No speaking of grama katha (nonsense)—One's order will never be disobeyed.
21) Eat food on the ground without dish or plate—One obtains a kingdom on Earth.
22) Chant the mantra Namo Narayana—One obtains the result of giving in charity 100 times.
23) Offer prayers to the Lord—One gets the result of giving cows in charity.
24) Touch the lotus feet of the Deity—One becomes a successful person.
25) Clean the temple of the Lord—If one is king he remains so for a Kalpa.
26) Circumambulating the temple three times offering prayers—At the time of death one will mount a swan airplane and go to Vaikuntha.
27) Singing or playing musical instruments in the temple of the Lord—One goes to Gardharvaloka.
28) Take pleasure in studying the sastras—One goes to Vishnuloka.
29) Sprinkle water in the temple—One goes to apsaraloka.
30) Take bath in a holy place—One's body becomes pure.
31) Worship Lord Vishnu with flowers—One goes to Vaikuntha.
32) Eat panchagavya—One gets the result of observing candrayana fasting.
33) Eat one meal a day—One gets the results of performing an Agnihotra.
34) Eat at night only—One gets the result of going to all the places of pilgrimage.
35) Eat at noon only—One attains Devaloka.
36) Take food not obtained by begging or any extraneous endeavor—One gets the results of opening water stands and digging wells.
37) Take bath daily—One will never see hell.
38) No eating on a plate—One gets the result of bathing at Pushkara
39) Eat on a leaf—One obtains the result of living at Kurukshetra.
40) Eat on a stone—One obtains the result of bathing at Prayog.
41) Giving up drinking to six hours—One will not be attacked by diseases.
42) During the Chaturmasya, garlands, caranamrta, candana and water from the conshell of the Lord, mahaprasädam, Deity garlands must be accepted.
In this way one who performs this vrata for the satisfaction of Lord Kesava becomes satisfied himself. O best of the Pandavas, among My devotees, he who accepts these vows and austerities during the Chaturmasya goes to my abode at the time of death, of this there is no doubt.
Vishnu Rahasya- Lord Brahma to Narada Muni.
Read more about vrata, sankalpa and Chaturmasya in general