The Prophet, Peace and Blessing of Allah be upon him, would not begin fasting Ramadan until there was a verified sighting of the crescent indicating the month or with the testimony of two trustworthy Muslim witnesses or just one witness. But when there was no sighting or testimony or the night of the thirtieth day of Sha'baan was cloudy and the crescent could not be sighted, he would complete thirty days for Sha'baan and then fast after that.
He, Peace and Blessing of Allah be upon him, would forbid that a Muslim fast a day or two days prior to the start of Ramadan out of precaution, unless those days coincided with days he normally fasted.
He, Peace and Blessing of Allah be upon him, would not break his fast until directly after the disk of the sun had disappeared. And he would order his Companions to hasten in breaking their fast. And he would break his fast before praying (the Maghrib prayer). He would break his fast with fresh dates. If he didn't find them, then with old dates and if he didn't find them, then with sips of water. When breaking his fast, he would say: "The thirst has gone, the veins have moistened and the reward is certain, if Allah wills." (Dhahaba Adh-Dhama'u wabtallatil-'urooqu wa thabatal-ajr in sha Allaah)
When he, Peace and Blessing of Allah be upon him, would travel in Ramadan, he would either fast or beak his fast and his Companions would choose between the two. So they would hold that whoever had energy and fasted then that was good and whoever was weak and broke his fast, then that was good.
It was from his, Peace and Blessing of Allah be upon him, practice, that Fajr sometimes would come on him while he was still in the state of Janaabah (sexual impurity), due to his wives, so he would bathe (make ghusl) after Fajr and then fast.
And he would kiss some of his wives while he was fasting in Ramadan, but he was the best amongst mankind at preventing his desires (from overtaking him).
He, Peace and Blessing of Allah be upon him, would use the Siwaak while fasting. And he would wash his mouth and nose while fasting, but would not let the water go deep in his nose or mouth.
He, Peace and Blessing of Allah be upon him, would pour water on his head during fasting, due to thirst or the heat.
He, Peace and Blessing of Allah be upon him, would eat dates for his pre-dawn meal (suhoor) and he would incite his Companions to take the Suhoor even if it was only a gulp of water. And he would delay the Suhoor until shortly before Fajr. The time between his Suhoor and the Fajr prayer was the extent it takes a man to recite fifty verses from the Book of Allah.