Archana is worship of the Lord. Those who perform the worship of Vishnu in this world, attain the immortal and blissful state of Moksha, thus says the Vishnu-Rahasya. Worship can be done either through an image or a picture or even a mental form. The image should be one appealing to the mind of the worshipper.
Worship can be done either with external materials or merely through an interior Bhava or strong feeling. The latter one is an advanced form of worship which only men of purified intellect can do. Worship should be done according to the rules laid down in the Varnashrama-Dharma or in the case of advanced devotees worship can be done in any manner they like. The purpose of worship is to please the Lord, to purify the heart through surrender of the ego and love of God.
Serving the poor people and worshipping saints is also worship of the Virat-Svarupa of the Lord. The Lord appears in all forms. He is everything. The scriptures declare that the Lord alone appears as the sentient and the insentient beings. The devotee should have Narayana-Bhava or Isvara-Bhava in all beings. He should consider all creatures, down even to the worm, as merely God. This is the highest form of worship.
Worship is generally done through the Tantrik or the Vaidika method. It can be done either in a temple or in one's own house, or even at any place outside. The object of worship is sincere devotion and real surrender for the sake of union with the Lord.
During worship the mind of the devotee should always be concentrated on the form of the Lord. It should think of His attributes, His Infinite Nature, Bliss, Immortality, etc. It should not think of earthly things.
The Bhog offered to the Lord during worship is actually taken away by Him when it is offered with sincere feeling. There are cases where devotees with burning love for God offered food to God and God actually appeared before them in His Supreme form and partook of the food offered to Him. These are rare cases, but it must be known that true devotees are very rare in this world.
Devotees like Prithu and Ambarisha practised this kind of Bhakti, i.e., Archana or worship of the Lord. Their stories are found in the Srimad-Bhagavata. The Lord appeared before Prithu, the first king of the world, and gave him His blessings. The Lord protected Ambarisha and gave him Emancipation. They were immersed in the love of God and they wanted nothing but God. They did not crave for worldly things from God but wanted only His grace. They wanted to please God and serve God. Nothing else did they want. Such should be the devotion of all Bhaktas of selfless motive.
Offerings to God need not necessarily be rich and costly things. What did the lord of elephants (Gajendra) offer? Only a flower from the tank. Draupadi offered a vegetable leaf and Sabari some wild plums. But the Lord was pleased. It is the feeling of love for God that God takes into account and not the material that is offered. He is pleased even with leaves and mere water.