An authentic Hadith indicates that fasting six days of Shawwal is Sunnah. It is not correct to oppose this Hadith with the reasons that some scholars cite for this fast being disliked such as the fear that an ignorant person might think that this is part of Ramadan or the fear that people may think this is obligatory.

There is nothing wrong fasting the six days of Shawwal on Mondays and Thursdays, and there will be recorded for you the reward of fasting the six days of Shawwal and of fasting on Mondays and Thursdays.

If you fast the six days of Shawwal, you do not have to fast al-Ayyam al-Beed during that month too and hopefully you will be rewarded for that.

Whoever fasts six days of Shawwal will have recorded for him a reward as if he had fasted a whole year. For more, please see the detailed answer.

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.

It is not a necessary condition that the six days of Shawwal should be fasted consecutively. If you fast them separately or consecutively, it is OK.

There is no basis for the false superstition about marriage in Shawwal. It is one of the leftovers of the Jahiliyyah (pre-Islamic era) when they used to be superstitious about that because of the connotations of the name of Shawwal which related to the drying up of the camel’s milk and the lifting of its tail.