The best fasting after Ramadan is fasting in al-Muharram. So, it is encouraged to fast a lot in the month of al-Muharram, not to fast the whole month.

1- Fasting on the first eight days of Dhul-Hijjah is recommended for pilgrims and others. 2- It is not Sunnah for pilgrims to fast on the day of ‘Arafah, rather it is recommended for them not to fast, even if they are able to fast.

You can start fasting six days of Shawwal from the second day of Shawwal because it is haram to fast on the day of ‘Eid.

1. If a person misses the fast of 'Ashura, it cannot be made up because there is no proof for that, and because the reward is connected to fasting on the tenth day of Muharram, and that time has passed. 2. If a person is excused for not fasting – such as women who are menstruating or bleeding following childbirth, or those who are sick or are travelling – and he usually fasts on that day or he had the intention of fasting that day, then he will be rewarded for his intention.

Fasting on the day of 'Ashura or `Arafah only expiates minor sins; as for major sins, they require sincere repentance. But falling into major sin does not mean that you should refrain from doing acts of worship and good deeds.