Sri Krishna Janmastami Vrata
During the daylight hours of the astami one should observe the vow of fasting in the association of devotees, and staying awake at night, at midnight one should perform the abhiseka according the vidhi just described, accompanied by joyful singing and dancing. The next day one should celebrate the Lord's appearance with great festivity and respect mahaprasadam with the vaisnavas.

One who performs worship of th Lord on Janmastami day according to the method stated above, and with the mood of service of the inhabitants of Vraja, will certainly gain the affection of Krsna. Having gained that affection he will be blessed with deep love of Krsna (prema) and will directly serve the Lord in Vrndavana eternally.

Janmastami Vrata:

     Janmastami, Vijaya Dasami, Dipavali, Rasayatra and Utthana Dvadasi were celebrated by
     Lord Caitanya.
                              CC Madhya v.6 p.17

     Vrajapura, the residence of Nanda Maharaja, was fully decorated with varieties of festoons and flags, and in different places, gates were made with varieties of flower garlands, pieces of cloth and mango leaves. The courtyards, the gates near the roads and everything within the rooms of the houses were perfectly swept and washed.
          SB 10.5.6

Fasting on this day is strongly advised. If one should eat on this day, the food one eats is equivalent to the meat of vultures, asses, crows and humans. As well as fasting one must engage in the worship of the Lord. As on ekadasi one may prepare the day before. On the astami one should begin the vrata by saying:

     adya sthitva niraharah sarva bhoga vivarjitah
     bhosye'ham pundarikaksa saranam be bhavacyuta

     Today I will renounce all food and tomorrow I will take.
     Please be my shelter, Acyuta.

Hari Bhakti Vilasa describes in detail the activities of the day, according to different puranas. Krsna Janma Abhiseka Vidhi by Srila Rupa Goswami gives a step by step description of Krsna's abhiseka in the evening. Elaborate appearance ceremonies of other deities may be modeled on this.

The Puranic description is as follows:

One can construct a house like a pregnancy room and decorate it with flowers, cloth and jewels. Murtis or pictures of the gopis, gopas, Nanda, Yasoda, Vasudeva, the Devatas, as well as the asuras (in sleeping state) should decorate the place.

One can draw a sarvatobhadra mandala, place a kumbha on it and place a metal plate over that filled with sesame. On that one should place the murti of Devaki with Krsna. One should carry out puja according to the vidhis, starting with the purvanga karmas (purificatory activities such as bhuta sudhi), manasa puja and ending with offering of external articles. One should use many flowers, much gandha and many varieties of fruits.

One should worship Devaki with the mantra "namo devyai sriyai".

After worshipping Krsna one should worship Vasudeva and others with "om vasudevaya namah" etc.

When the moon rises one should offer arghya to the moon saying:

     ksirodarnava sambhuta atrinetra samudbhava
     grhanarghya sasankesa rohinya sahito mama

     jyotsnapate namastubhyam namaste jyotisam pate
     namaste rohini kanta arghyam me pratigrhyatam

Then offer arghya to Krsna:

     jatam kamsa vadharthaya bhu bharottaranaya ca
     devatanam hitarthaya dhara samsthapanaya ca
     kauravanam vinasaya daityanam nidhanaya ca
     grhanarghyam maya dattam devaki sahito mama
     sri krsnaya devaki sahitaya saparibaraya

     laksmi sahitaya arghyam namah

One may then perform full puja of Krsna according to the rules using the mantras:

etat padyam (footwater) om yajnesvaraya yajna sambhavaya yajna pataye govindaya namo namah

idam snaniyam (bath) om yogesvaraya yoga sambhavaya yoga pataye govindaya namo namah

idam vastram (cloth) om yajnesvaraya yajna sambhavaya yajna pataye govindaya namo namah

idam alankaram (ornaments) om yajnesvaraya yajna sambhavaya yajna pataye govindaya namo namah

esa dhupah (incense) om yajnesvaraya yajna sambhavaya yajna pataye govindaya namo namah

esa dipa (lamps) om yajnesvaraya yajna sambhavaya yajna pataye govindaya namo namah

idam naivedyam (food) om visvesvaraya visva sambhavaya visva pataye govindaya namo namah

idam tambulam (betal nut and spices) om dharmesvaraya dharma sambhavaya dharma pataye govindaya namo namah

The next day one should feed the brahmanas and give gifts.