NIQABI , AS THE WOMEN OF PARADISE

IT SHOULD COVER ALL THE BODY

O Prophet! Tell your wives and your daughters and the women of the believers to draw their cloaks (veils)* all over their bodies (i.e. screen themselves completely except the eyes or one eye to see the way).  That will be better, that they should be known (as free respectable women) so as not to be annoyed.  And Allah is Ever Oft-Forgiving, Most Merciful. (Al-Ahzab 33:59)

Al Haafiz Ibn Katheer, said in his Tafseer: This means that they shoul not display any part of their adornment to non mahrams, apart from that which it is impossible to conceal.
 IT SHOULD NOT BE  AN ADORNMENT IN AND OF ITSELF

Allah(Subhanna wa ta'ala) said:(interpretation of the meaning)

"....and not to show off their adornment..."(An Noor,31)

The general meaning of this phrase includes the outer garment, because, if it is decorated it will atract men's attention to her.

One ayah in Surah Al Ahzaab, suppor it:

(interpretation of the meaning)"...And stay in your houses, and do not display your selves like that of the time of ignorances..."(Al Ahzaab,33)

 IT SHOULD BE THICK AND NOT TRANSPARENT OR SEE THRU

The Prophet (Sala allahu alaihi wa salam) said.
"During the last days of my Ummah, they will be women who are clothed but naked, with something on their heads like the humps of camels. Cursem , for they are cursed (Al Bukhari)
Other hadith said:
"They will not enter Paradise  or even small its fragance, althougts its fragance can be detected from such and such distance"(Muslim)

Al Suyooti in Tanweer al Hawaalik 3/103 narrated that

Ibn 'Abd  al Barr said: " What the Prophet (Sala Allahu alaihi wa salam ) meant was women who wear clothes made of light fabric

which describes and does not cover.They are clothed by name but naked in reality.

 IT SHOULD BE LOOSE NO TIGHT

The purpose of clothing is to prevent Fitnah( temptation) and this can only be achieve if clothes are wide and loose.

Usaamah Ibn Zayd said :"The messenger of Allah(Sala Allahu alaihi wa salam) give me a thick egyptian garment that was one of the gifts given to Him by Duhyat al Kalbi, and I give it to my wife to wear. He said:Why do I not see you wearing that egyptian garment?
I said: I give it to my wife to wear. He said: Tell her to wear a gown underneath it , for I am afraid that it may describe the size of her bones.( By al Diyaa al Maqdisi in  al Ahaadeeth  al Mukhtaarah)
 IT SHOULD NOT BE PERFUMED
Abu Moosa al Ashari said:(The messenger of Allah(Sala Allahu alaihi wa salam) said: Any woman who puts on perfume then passes by people so that they can smell her fragance is an adulte.(Dawud)
The reason for this prohibition is quite clear, which is that, woman's fragancemay cause undue provocation of desires.
 IT SHOULD NOT RESEMBLE THE CLOTHING OF  MEN 
Ibn Abbas said:The Prophet(Sala Allahu alaihi wa salam) cursed effeminate men and masculine women, He said:" Thrown them out of your houses".
Ibn Abi Maleekah said:It was said to Aisha (Radia Allahu anha) "What if a woman wears men's sandals? she said: The
Messenger of Allah(Subhanna wa ta'ala) cursed woman who act like man.

.This hadiths, indicated that is forbidden for a woman to imitate man and vice versa.

IT SHOULD NOT RESEMBLE THE DRESS OF KAAFIR

Muslims , man and woman alike, they should not  imitate the kufaar.

"Verily , Allah will not change the condition of people as long as they do not change their state themselves..."(interpretation of the meaning of  Ar Rad:11)

IT SHOULD NOT BE A GARMENT OF FAME AND VANITY

Ibn Umar (Radia Allahu anhu) said: The messenger of Allah (Sala Allahu alaihi wa salam) said: whoever wears a garment of fame and vanity in this world, Allah will clothe him in a garment of humiliation on the Day of Resurrection, then He will cause Fire to flame up around him.

Source: Jilbab al Marah al muslimah of Shaikh Albani.

Summary text.