The thali
Prepare a plate with the rakhis, roli or kumkum, rice, a ghee lamp, sweets and a little water. First offer a rakhi to the family deity or to Ganesha, and pray for the protection of all the family.
Tying the rakhi
The brother sits facing east, with a cloth or handkerchief on his head. The sister applies a tilak of roli and rice to his forehead, and ties the rakhi on his right wrist while saying the mantra: "Yena baddho Bali raja danavendro mahabalah, tena tvam pratibadhnami rakshe ma chala ma chala." It means: "With this I bind you, as the mighty Bali, king of the danavas, was bound; O protection, do not waver, do not waver."
She performs aarti for him with the lamp, feeds him a sweet and prays for his long life and well-being. The brother gives her a gift and promises to protect her, and touches the feet of an elder sister or receives the touch of a younger one.
Bhadra
Bhadra, also called Vishti karana, is held inauspicious for tying the rakhi: the story goes that Ravana's sister tied his rakhi during Bhadra, and he lost his kingdom. When Bhadra falls on Shravana Purnima, the rakhi is tied after it ends. The Raksha Bandhan date page gives the times for your city.