This article is by Sukhmandir Kaur, a respected source.
Ardas is prayer of supplication performed by a Sikh. The word Ardas means to petition. Prayer may take the form of a request, an entreaty, or of an offering.
Too thakur tum peh ardaas||
"You are Lord Master; to You, I offer this prayer". (Sri Guru Granth Sahib Ji||268)
Ardas is offered
Before prakash, the ceremonial opening of the Sikh scripture Guru Granth.
During a worship service, or other Sikh ceremony such as a wedding or a funeral, prior to selecting a hukam, a random verse from the Guru Granth which is considered to be the Guru's order.
After sukhasan, the ceremonial closing of the Guru Granth.
Whenever a Sikh wishes to communicate with the divine.
Ardas is a structured petition which addresses:
Each of the ten gurus by name.
The Sikh scripture Guru Granth.
Waheguru, (the Sikh name for God).
The Panj pyara, administers of Sikh baptism.
Sikh martyrs and their sacrifices.
The Sikh places of worship.
Ardas asks for pardon of mistakes, fulfillment of objectives, company of like minded souls, and prosperity of all persons.
Ardas is concluded with a salutation by all present of, "Waheguru ji ka Khalsa Waheguru ji ki Fateh," which means the Khalsa, or initiated Sikhs, belong to God. Victory belongs to God.
This address is followed by who are all present calling out, "Sat Siri Akal," and is directed to the immortal enlightener, who is the destroyer of darkness.
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Examples:
Ardas is performed while standing with hands pressed together.
The person offering ardas and all persons present stand with hands folded facing the Guru Granth.
The attendant of Guru Granth continues to hold and wave a fly whisk while standing.
When ardas is performed with out Guru Granth Sahib present, every one stands together and faces any direction.
When a specific ardas is performed for one or more persons, others are not required to stand.
"Du-e kar jor karao ardaas"||
"With my palms pressed together, I offer this prayer."(Sri Guru Granth Sahib Ji||1152)
http://sikhism.about.com/od/glossary/g/Ardaas.htm