Fasting Six Days of Shawwaal

Abu Ayyoub reported that the Messenger of Allah, salla Allahu alaihi wa sallam said �Whoever fasts the month of Ramadhan and then follows it by fasting six days during the month of Shawwal will be rewarded as if he had fasted the entire year. 

(Saheeh Muslim)

Fasting Six Days of Shawwaal (The ClearSunnah.Blog)
The reward of fasting the six days of Shawwaal, the manner of observing this voluntary fast

Excerpts:

Fasting the six (days) of Shawwaal is a recommended act of worship and not an obligation.

It is not a must for him to fast immediately after �eed al-fitr, rather it is permissible to begin fasting after �eed by a day or (a number of) days. And (also) to fast them continuously or intermittently in the month of Shawwaal according to that which is easy for him. And the issue is quite open in this matter, and it is not obligatory, rather it is a sunnah.

"These days can be anytime during the month of Shawwal except the first day because it is unlawful to fast the day of Eid. These days do not have to be at beginning of the month nor do they have to be consecutive. Hence, Muslims should seize this opportunity and fast these six days to get Allah�s reward."

He should not do the voluntary fast whilst he has a day or days to make up from Ramadhaan. Rather, he should begin by making up that which he has (outstanding) from Ramadhaan, then do the voluntary fast.

• Fasting the six days of Shawwal while still having to make up fasts
• Fasting the six days of Shawwal after the month of Shawwal has ended

Related:
TJ Printable: Fasting Other Than Ramadan
Voluntary Fasting in Islam - Salafi Publications