How are the flags raised outside the UN Headquarters in New York?

The flags are raised manually by UN Security officers every weekday morning at approximately 8am and lowered every weekday at around 4pm, except in the cases of bad weather. The flags are organized in English alphabetical order from north to south. On weekends, only the UN flag is raised. Further information can be found in this 1992 article from the UN Chronicle:

"So Proudly They Wave ... Flags of the United Nations", Endrst, Elsa B. UN Chronicle, Vol. 29, No. 4 (December 1992)

On 10 September 2015, the General Assembly adopted A/RES/69/320 on Raising the flags of non-member observer States at the United Nations. 

• The flag of the Holy See was raised by the UN for the first time on 25 September 2015, to coincide with the arrival of Pope Francis to the UN.
• The Palestinian flag was raised for the first time on 30 September 2015, when Mahmoud Abbas delivered remarks to the General Debate.