THE AMOUNT OF DHIKR YOU SHOULD DO
Allah, the Exalted, ordered that He should be remembered a lot. Describing the wise men and women who ponder His signs, the Qur'an mentions,
"those who remember Allah standing, sitting, and on their sides,"
[AL-IMRAN, 3:191] and
"those men and women who engage much in Allah's praise. For them has Allah prepared forgiveness and a great reward." [AL-AHZAB, 33:35].
Mujahid explained, "A person cannot be one of `those men and women who remember Allah much' as mentioned in the above verse of the Qur'an, unless he or she remembers Allah at all times, standing, sitting, or lying in bed."
When asked how much Dhikr one should do to be considered as one of "those who remember Allah much," Ibn Al-Salah said that "much" is "when one is constant in supplicating, in the morning and evening and in other parts of the day and the night as reported from the Prophet, peace be upon him."
Concerning the above Qur’anic verses Ali Ibn Abi Talha relates that `Abdullah Ibn `Abbas [R.A.] said, "All obligations imposed upon man by Allah are clearly marked and one is exempted from them in the presence of a genuine cause. The only exception is the obligation of Dhikr. Almighty Allah has set no specific limits for it, and under no circumstances is one allowed to be negligent of it. We are commanded to `remember Allah standing, sitting, and reclining on your sides,' in the morning, during the day, at sea or on land, on journey or at home, in poverty and in prosperity, in sickness or in health, openly and secretly, and, in fact, at all times throughout one's life and in all circumstances."
Imam Ibn Qayyim mentions in his book “Al Waabil As-Sayyib” that one who is frequently engaged in Dhikr, whether he is in or out of his house, whether he is stationary or travelling, he will find on the Day of Judgement a large number of witnesses in his favour. The Messenger of Allah [S] said, “Whatever deed is done, good or bad, by any man or woman on the face of the earth, the earth will describe it all, with date, time and place.”
Hence, one who does Dhikr at many places will find many witnesses. It is therefore very important that we strive to do as much Dhikr as possible, and in as many places as possible.
Almighty Allah states in the Holy Qur’an:
And remember Allah much that you may prosper. 
WADH- KURUL-LĀHAKA-THĪRAN LA`ALLAKUM TUFLIHŪN
[ SŪRAH AL-JUMU`AH, 62:10 ]
And remember the name of your Lord at morning and evening,
And prostrate yourself unto Him a part of the night, and glorify Him through a long night. 
WADH- KUR- ISMA RABBIKA BUKRATAN WA ASĪLAN
WA MINAL- LAYLI FAS-JUD LAHŪ WA SABBIH-HU LAYLAN TAWĪLAN
[ SURAH AD-DAHR / AL-INSĀN, 76:25-26 ]
 SŪRAH AL-JUMU`AH, 62:10
 SURAH AD-DAHR / AL-INSĀN, 76:25-26