Gayatri mantra is one of the oldest and most powerful of Sanskrit mantras. It is believed that by chanting the Gayatri mantra and firmly establishing it in the mind, if you carry on your life and do the work that is ordained for you, your life will be full of happiness

"Aum Bhuh Bhuvah Svah Tat Savitur Varenyam Bhargo Devasya Dheemahi Dhiyo Yo nah Prachodayat"
Gayatri mantra is one of the oldest and most powerful of Sanskrit mantras. It is believed that by chanting the Gayatri mantra and firmly establishing it in the mind, if you carry on your life and do the work that is ordained for you, your life will be full of happiness. It rescues the chanter from all adverse situations that may lead to mortality. Goddess Gayatri is also called "Veda-Mata" or the Mother of the Vedas - Rig, Yajur, Saam and Atharva - because it is the very basis of the Vedas. There are 26 deities mentioned in the Gayatri Mantra.
Tat ~ Ganesha
Sur ~ Narsimha
Vi ~ Vishnu
Tu ~ Shiva
Va ~ Krishna
Re ~ Radha
Ni ~ Lakshmi
Yam ~ Agni
Bha ~ Indra
Rga ~ Saraswati
De ~ Durga
Va ~ Hanuman
Sya ~ Prithvi
Dhee ~ Surya
Ma ~ Sriram
Hi ~ seeta
Dhi ~ Chandra
Yo ~ Yama
Ya ~ Brahma
Na ~ Varuna
Cho ~ hayagreeva
Da ~ Hamsa
Yaat ~ Tulsi

Best time to chant it is when all stars are seen in the sky before Sunrise. Medium time is when stars meet sun in the morning and evening. Worst time is when starts disappear from the sky and only sun is there. That's why ancestors practised mantras before Sunrise at 4am. One should chant 1008/ 108 / or atleast 10 times a day!
Subah uthkar 8 baar jap kijiye , Asht karmo Ko jeetne ke liye.
Bhojan ke samay EK baar, Amrit ke samaan bhojan prapt karne ke liye.
Bahar jaate samay 3 baar, Smridhi, safalta Aur siddhi ke liye.
Mandir mein 12 baar, Prabhu ke guno Ko yaad karne ke liye.
Cheenk aaye toh EK baar jap kijiye, amangal duur karne ke liye.
Sone Se Pehle 7 baar, Saat prakaar ke Bhay duur karne ke liye.