1. Sanity.
2. Islam: Should be a Muslim and follow Islamic laws.
3. For women - they must remain free from Haiz and Nifas for the whole day.
4. Not being in danger of illness by fasting.
5. Not being a traveller.

Saum is an act of worship; its main purpose is to abstain from forbidden things so as to earn "the pleasure of Allah by obeying Him."

The most important thing is the Niyyat (Intention). There is no need to utter it. However one must have in mind why one is fasting; that is one must have in mind: "Qurbatan Ilallah"; for the pleasure of Allah.

Niyyat can be made for the whole month together on the eve of the first of Ramadhan or individually on the eve of each day. If you choose to do Niyyat for the whole month together, then if you miss a fast for any reason in between, you will be required to do Niyyat again.

Fasting begins with the setting in of the time for Subh prayers. This time is called SUBHE SADIQ or FAJR. Fasting ends at MAGHRIB which occurs a few minutes after sunset.