Vaikhanasa Agama( Antaryaga vs Bahiryaga, Amurta and Samurta aradhana)

According to the Vaikhanasa agamas, worship of the lord can be done either internally ( antaryaga) or externally(bahiryaga). A person who is interested in doing antaryaga should get up before sunrise by gaining mastery over sleep. After that he should finish his morning cleaning rituals facing east or north. He should clean his toungue, teeth and take bath and become clean. After that he should wear the urdhva pundra of the Lord. After that anganyasa and karanyasa ( any of the variations can be followed) should be done by reciting the appropriate mantras. He should seat himself in front of the Lord by either facing east or north. Atma suktam should be recited carefully and the sadhaka should identify himself with the Supreme soul. Pranayama should be done with all its limbs like rechaka, puraka and kumbhaka after this. After this he should think of a 16 petalled lotus in his heart and write all the necessary beejas in all the sixteen petals. Otherwise an eight petalled lotus can be meditated upon by writing the eight sacred letters. ( Like the eight letters of the ashtakshari " Om Namo Narayanaya"). Inside that lotus, the fields of Sun, Moon and Fire should be meditated upon. In the core of the fields, one should meditate upon the Supreme Lord Vishnu in the form of the letter "Om". The Lord should be thought of as same as the sound "Om". The Lord should be thought of as this single letter "Om" as mentioned in the sruti vakyam "sa brahma ...." . ( "The Pranava om is verily Brahma, it is verily Siva, it is verily Vishnu and it is the Supreme Lord" is the gist of that sruti vakyam for those who havent heard this). The Lord should be meditated upon incessantly depending on one's sradha for as much time as possible as "Om" which is in the form of a flame of length one inch. Thus one should merge himself in that flame, which is verily the Supreme Lord Vishnu, who is same as the pranava. This kind of worship is not easily accessible to lesser intelligent people. Now follows the bahiryaga.
Bahiryaga is very simple and is easily doable by anyone. The Lord should be installed in the form of an Archa image by installing the Bija(om can be used if one is not initiated) in the heart of the image first. He should then be worshipped using the regular ways like offering flowers, giving food, reciting stotras etc. That Lord who is thus worshipped everyday is verily the Eternal one and fulfills all the desires of His devotees. The gist is that worshipping Lord in the form of an external image is very useful when one is not in an advanced spiritual stage.
As far as the temple worship is concerned, the Vaikhanasa agamas prescribe two ways of worship. Amurtam (without form) - this is that part of worship where the Lord is worshipped in the Vedic fires / Sun / Heart / Water / Earth through offerings of ghee etc. Samurtam - This is the worship that is done to the Lord in the form of an archa image in the temple. In any Vishnu temple which follows the Vaikhanasa style both amurtam and samurtam are used in the right mixture.
(This is not specific only to Vaikhanasa agamas but is seen in other agamas like Sakti etc. The general opinion that Vedic followers do not understand formless worship is very false. The meditation based on Agni, Soma and Surya mandalas is very extensively used in Sakti worship based on Kundalini. Sakti worshippers divide the spiritual centres into Agni( bottom two chakras), Surya(next two till heart) and Soma( the next two) . But Vaikhanasas put all the three mandalas in heart itself? Is one of them wrong? There is no contradiction here as the meditations are not related to the physical body and are really meant to meditate on the Agni,Surya and Soma mandalas one after another. One can clearly see that both the Vaikhanasa and Sakti styles achieve the same result. Another interesting observation. The Supreme has created this Universe in such a way that what is inside is replicated in a macro scale outside. See for example Fire gives energy to Sun, who in turn makes the moon shine. )