Witr prayer is one of the greatest acts of worship that draw one closer to Allaah.  It is one of the confirmed Sunnahs (Sunnah mu’akkadah) which the Muslim should observe regularly and not neglect. 

Witr starts when a person has prayed Isha. Prophet (SAW) said: “Allah has prescribed for you a prayer (by which He may increase your reward), which is Witr; Allaah has enjoined it for you during the time between Isha Salah until dawn begins.” [al-Tirmidhi: 425]
Most Muslims perform Witr along with Isha. Although it is not wrong, the Sunnah indicates a differnet concept that what most Muslims do. Prophet Muhammad (SAW) said: “Whoever fears that he will not get up at the end of the night, let him pray Witr at the beginning of the night, but whoever thinks that he will be able to get up at the end of the night, let him pray Witr at the end of the night, for prayer at the end of the night is witnessed (by the angels) and that is better.” [Muslim: 755]

Many Muslims, do not know how to perform it in the manner performed by Prophet Muhammad (SAW). Also, most of them think Witr only consists of 3 raka'at. But it can consist of 1,3,5,7,9 or 11 raka'at. 

-- Two ways of performing 3 raka'at:
1. To pray them one after another, with one tashahhud. Aa’ishah (RA) said: The Prophet (SAW) used not to say the tasleem in the (first) two rakahs of Witr. According to another version: “He used to pray Witr with three rak'ahs and he did not sit except in the last of them.” [al-Nasaa’i, 3/234]
2.  Saying the tasleem after two rak'ahs, then praying one rak’ah on its own. Ibn ‘Umar (RA) used to separate the two rak'ahs from the single rak'ah with a tasleem, and he said that the Prophet (SAW) used to do that. [Ibn Hibbaan 2435]

--To perform 5 or 7 raka'at:
The raka'at should be continuous, and one should only recite one tashahhud in the last of them and say the tasleem. ‘Aa’ishah (RA) said: The Messenger of Allaah (SAW) used to pray thirteen rak’ahs at night, praying five rak’ahs of Witr, in which he would not sit except in the last rak’ah. [Muslim 737]

--To perform 9 raka'at:
Aa’ishah (RA) said: Prophet (SAW) used to pray nine raka'at in which he did not sit except in the eighth, when he would remember Allaah, praise Him and call upon Him, then he would get up and not say the tasleem, and he would stand up and pray the ninth (rak’ah), then he would sit and remember Allaah and praise Him and call upon Him, then he would say a tasleem that we could hear. 

--To perform 11 raka'at:
If one prayed Witr with eleven rak’ahs, he/she should say the tasleem after each two rak’ahs, then pray one rak’ah at the end. 

All these ways of offering Witr prayer have been mentioned in the Sunnah, but the best way is not to stick to one particular way; rather one should do it one way one time and another way another time, so that one will have done all the Sunnahs.

 
If I made any mistakes, it was from Shaytan and my own mistakes. If anything you find is useful, is from Allah as He guides whom He wills.
JazakAllahu Khairan. BarakAllah Fekkum and Salam...