1) The intention (niyyah) for Ramadan fasts is made at night, before the dawn comes. The Prophet (peace be upon him): “Whoever does not intend to fast from the night before, there is no fast for him.” (al-Nisaa’i; classed as hasan by al-Albani) Whoever does not resolve to do so, his fast is not valid. The correct intention is when a person resolves in his heart that he is going to fast tomorrow. It is not prescribed for him to utter it out loud.
2) The “day of doubt”: when people are not sure whether it is the last day of Sha’ban or the first of Ramadan because of cloudy weather or another reason. Fasting on this day is haraam. The Prophet (peace be upon him) said: “Fast when you see the new moon abd break your fast when you see the new moon, and if you are not sure then complete Sha’ban as thirty days.” (al-Bukhari)
3) The Prophet (peace be upon him) said: “Do not preempt Ramadan by one or two days, except for those who have the habit of fasting regularly, in which case they may fast.” (al-Bukhari). A person may also fast if he is bound by a vow or has to make up an obligatory fast. Fasting at the end of Sha’ban is prohibited to maintain a distinction between the obligatory and voluntary fasts.
4) Zakaah must be paid immediately when one full hijri year has passed since the nisaab [minimum threshold] is acquired. If a person pays it in advance in Ramadaan before the year has passed (to take advantage of the virtue of the month), there is nothing wrong with that. But after the year has passed it is not permissible to delay it until Ramadaan. Zakaah on agricultural crops must be paid on the day of harvesting.
5) One of the conditions of zakaah is having the proper intention at the time of paying it. It is not acceptable to decide that what one has previously given (with the intention of sadaqah) is now zakaah.