What Is Salat al-Hajah?
Question

My question has to do with praying to Allah for a need. I know it is called salat al-hajah. How many times does a person have to pray it and when should it be prayed. Is it right to pray it at the times when dua’s are most likely to be
Praise be to Allah.Worship Allah the Prophet’s way
It is prescribed for the Muslim to worship Allah in the ways that He has prescribed in His Book, and in the ways that have been proven from the Prophet (peace and blessings of Allah be upon him). The principle concerning matters of worship is tawqeef [i.e., following what is in the Quran and sahih Sunnah; with no room for individual opinion]. And we cannot say that any act of worship is prescribed unless there is sahih evidence.
What is Salat al-Hajah?
The so-called Salaat al-Hajah was narrated in da’if (weak) or munkar (denounced) ahadith – as far as we know – which cannot be used as proof and which are not fit to base acts of worship on. (Fatawa al-Lajnah al-Daimah, 8/162)
Degree of the Hadith about  Salat al-Hajah
The hadeeth narrated concerning Salat al-Hajah says:
“From ‘Abd-Allah ibn Abi Awfa al-Aslami, who said: The Messenger of Allah (peace and blessings of Allah be upon him) came out to us and said: ‘Whoever has need of something from Allah or any one of His creation, let him do wudu’ and pray two rak’ahs, then let him say, “There is no god but Allah, the Forbearing, the Most Generous. Glory be to Allah, Lord of the mighty Throne. Praise be to Allah the Lord of the Worlds. O Allah, I ask You for Your mercy and forgiveness and I ask You for all good things and for safety from all sins. I ask You not to leave any sin without forgiving it, or any distress without relieving it, or any need which it pleases You to fulfil without fulfilling it for me.” Then let him ask Allah for whatever matter of this world or the Hereafter that he wishes, for it will be fulfilled.” (Narrated by Ibn Majah, Iqamat al-Salah wa’l-Sunnah, 1374)
Al-Tirmdihi said: “This is a ghareeb [strange] hadeeth, and concerning its isnad it was said: Faid ibn ‘Abd al-Rahman is weak in hadith.
Al-Albani said: rather it is da’if jiddan (very weak). Al-Hakim said: mawdu’ (fabricated) ahadith were narrated from Abu Awfa. (Mishkat al-Masabih, vol. 1, p. 417)
The author of al-Sunan wa’l-Mubtada’at said, after mentioning what al-Tirmidhi said concerning Faid ibn ‘Abd al-Rahman: Ahmad said he is matruk (left, i.e., his hadith is not to be accepted), and Ibn al-‘Arabi described him as da’if (weak). 
And he said: “You know what is said concerning this hadith. It is better and more perfect and safer for you to  make du'a’ to Allah in the depths of the night and between the adhan and iqamah and at the end of every prayer before the taslim; and on Fridays, for then there are times when dua’ is answered; and when breaking one’s fast. For your Lord says (interpretation of the meanings): 
‘Invoke Me [i.e. believe in My Oneness (Islamic Monotheism) and ask Me for anything] I will respond to your (invocation)’ [Fussilat 40:60]
‘And when My slaves ask you (O Muhammad) concerning Me, then (answer them), I am indeed near (to them by My Knowledge). I respond to the invocations of the supplicant when he calls on Me (without any mediator or intercessor)’ [al-Baqarah 2:186]
‘And (all) the Most Beautiful Names belong to Allah, so call on Him by them’ [al-A'raf 7:180].” (Al-Sunan wa’l-Mubtada’at by al-Shuqayri, p. 124)