The Methods of Dhikr, Remembrance of Allah
 
There are a number of hadiths which are directly relevent to the methods of dhikr used by various Sufi turuq. I have grouped them below, under the titles "Posture is Irrelevent to Dhikr," "Dhikr in Assembly and in a Circle," "Dhikr Saying `La ilaha illa Allah,'" "Dhikr by saying `Allah,'" and "No Limits to doing Dhikr." 

Posture is Irrelevent to Dhikr 

The Qur'an says in meaning: 

Lo! In the creation of the Heavens and the earth and in the night and day are tokens (of His sovereignty) for men of understanding, such as remember Allah, in standing, sitting, and reclining.  [Qur'an 3:190-191]
What this part of the Qur'an establishes is that posture is not important in performing dhikr - standing, sitting, or reclining. Presumably other postures are also okay, so criticisms about posture during dhikr is irrelevent. 

Dhikr in Assembly and in a Circle 

The following ahadith is about those Sahaba who did dhikr in assembly and in a circle, and were praised by Rasulullah (s.a.w.) for it: 

Hadhrat Abu Sa`eed Khudri relates that once Hadhrat Mu`awiyah visited the mosque and saw a circle (of reciters). He asked, 

"What has made you sit?" 

They said, "We have assembled here to remember Allah." 

He [Mu`awiyah] said, "By Allah you did not sit except for this purpose?" 

They affirmed, "We did not sit except for this." 

Hadhrat Mu`awiyah then told them, "I did not ask you to swear on account of any malice. None of you can match me for scanty narration of the Prophet (s.a.w.) (and as such have narrated very few traditions about him). The Holy Prophet (s.a.w.) once visited a gathering of his companions and inquired, 

`What has made you assemble here?' 

They answered, `We have gathered to remember Allah and praise Him for having led us to Islam and granted this favour to us.' 

The Holy Prophet (s.a.w.) inquired, `Do you affirm by Allah that it is so?' 

The Holy Prophet's Companions affirmed, `By Allah we are sitting here for this purpose only.' 

He [the Prophet s.a.w.] said, `I have not put you on oath on account of any doubt, but angel Jibreel had visited me and told me that Allah felt proud of you among the angels.'"

[From Sahih Muslim, and also in the Riyadh us-Saliheen of Imam Nawawi.] 

Here is another hadith, which shows the benefit of doing dhikr in assembly. 

Ibn `Umar reported, "The Prophet, peace be upon him, said, `When you pass by a garden of paradise, avail yourselves of it.' The Companions asked, `What are the gardens of Paradise, O Messenger of Allah?" The Prophet, peace be upon him, replied, `The assemblies of dhikr. There are some angels of Allah who go about looking for such assemblies of dhikr, and when they find them they surround them.'"
[Quoted from Fiqh us-Sunnah compiled by As-Sayyid Sabiq, vol. 4, ch. 6.] 

There is also this important hadith about dhikr in general, and dhikr in an assembly: 

On the authority of Abu Hurayrah (may Allah be pleased with him), who said that the Prophet (may the blessings and peace of Allah be upon him) said: Allah the Almighty says: 

I am as My servant thinks I am. I am with him when he makes mention of Me. If he makes mention of Me to himself, I make mention of him to Myself; and if he makes mention of Me in an assembly, I make mention of him in an assembly better than it. And if he draws near to Me a hand's span, I draw near to him an arm's length; and if he draws near to Me an arm's length, I draw near to him a fathom's length. And if he comes to Me walking, I go to him at speed.

[It was related by al-Bukhari, and also by Muslim, at-Tirmidhi and Ibn Majah.  From "Forty Hadith Qudsi," selected and translated by Ezzeddin Ibrahim and Denys Johnson-Davies (Dar Al-Koran Al-Kareem, Lebanon, 1980), hadith no. 15.] 

Doing Dhikr by saying "La ilaha illa Allah" 

One of the ways of doing dhikr is by saying "La ilaha illa Allah." Here are some hadiths which mention this.... 

Hazrat Jabir relates that he heard the Holy Prophet (s.a.w.) having said: 

"The best remembrance of Allah is `La ilaha illa Allah.'"

[From Tirmidhi, also related in the Riyadh us-Saliheen of Imam Nawawi] 

Another hadith about saying `La ilaha illa Allah' for dhikr is this.... 

Abu Hurairah reported that the Prophet, peace be upon him, said, "Renew your faith." "How can we renew our faith?" they asked. The Prophet, peace be upon him, said, "Say always, `La ilaha illa Allah'."
[From Ahmad, with a sound isnad. Quoted in Fiqh us-Sunnah compiled by as-Sayyid Sabiq, vol. 4, ch. 6.] 

Doing Dhikr by saying "Allah" 

Regarding using the names of Allah in dhikr, the hadith I am aware of at present regarding this topic is the following.... 

The Prophet said, "The Hour will not arise before `Allah, Allah' is no longer said on earth."
[Sahih Muslim] 

No Limits to doing Dhikr 

Now, some criticize those on the Sufi path for doing too much dhikr. However, Ibn Abbas (r.a.) is related as having said there is no limit to dhikr. 

The following quote I took from the book "Fiqh us-Sunnah" by as-Sayyid Sabiq. The saying of Ibn Abbas goes.... 

Ali b. Abi Talha relates that Ibn Abbas 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 obligatin of dhikr. 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,' [Qur'an 3:191] 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."
Dhikr is a very blessed practice, praised in the Qur'an and hadiths. 

May Allah help bring us satisfaction in our hearts through remembrance of Him. 

Say: "Truly Allah leaves to stray whom He will, but He guides to Himself those who turn to Him in penitence -- Those who believe, and whose hearts find satisfaction in the remebrance of Allah, for without doubt in the remembrance of Allah do hearts find satisfaction[Qur'an 13:27-28]