Which is better regarding voluntary fasting: to do a lot of it, or to fast one day and break the fast the next, or to fast specific days such as the White Days, Mondays, and Thursdays, and some scattered days?

The matter of voluntary fasting is broad, and one should not adhere to what has not been established. Among the best forms of fasting is the fasting of David, peace be upon him. The Prophet, may Allah bless him and grant him peace, used to fast on Mondays and Thursdays because deeds are presented on those days. He also encouraged fasting on the White Days (Ayyam al-Bid), and he would sometimes fast consecutively and sometimes break his fast consecutively, but he never abandoned fasting on Mondays and Thursdays.