Poojaa means devotional worship. Atri Sanhitaa mentions two types of worship - visible or Moort having a shape and form and invisible A-Moort that which has no shape. Vaidik Agni Worship is A-Moort and is for more imaginative people; but for the less imaginative people visible form of worship (Moort) Poojaa was introduced at a later date. On later dates it developed into various Avataar and other Devtaa. Conception of a particular shape, color and demeanor has greater effect on the mind of a true devotee in developing a particular Ras or emotion. This partly accounts for the multiplicity of the same Deity in different forms, colors and attitudes.

A Hindu has the freedom to choose his own way of worshipping God..

(1) Poojaa can be performed with a Hom (Yagya), which consists of kindling a fire, chanting Mantra in front of it, and oblations to God by pouring them into fire. Here fire acts the messenger-priest who communicates the message of the man to God.

(2) Poojaa can be done by reciting favorite hymns sitting in front of an image of God often followed by an Aaratee (by waving a lamp, burning an incense, and offering flowers, fruits, sweets, Tulasee or Bilva leaves, and water in front of that person or God's idol with reciting or not reciting a hymn).

(3) It may consist of repeating the name of God, loudly or quietly, 108 times or more. This name of God can be only name of God, a Mantra (for example Gaayatree Mantra), or a short phrase, such as "Om Namah Shivaaya" etc.

(4) It may be done individually in a lonely place at home, or in congregation by singing devotional songs and Mantra followed by Aaratee and offering as above.

(5) It may even consist of Aavaahan (invoking God) of the deity in one's home, offering Him a seat, washing His feet, offering Him perfume and incense, lighting a lamp to show Him one's happiness at His arrival, offering flowers and food and lastly Aaratee.

On special days a Poojaa is accompanied by fasting and eating special vegetarian food first offered to God.

Naarad Jee said to King Ambareesh - Learned man should worship Hari by putting Havishya in Agni (fire), by flowers in water, by meditating in mind, and by Jap in solar system.

First Ahinsaa, second control on Indriyaan, third to be kind on all living beings, fourth forgiveness, fifth Sham, sixth Dam, seventh meditation, and eighth Truth - these are eight flowers. Other flowers are only for show, Krishn is pleased with only above mentioned flowers. Water is the flower of Varun Devtaa. Ghee, milk and yogurt are the flowers for Chandramaa. Grains is the flower for Prajaapati, Dhoop and lamp for Agni Dev and fruits and flowers are for vegetation. Kush and roots are the flowers for Prithvi, smell and sandalwood are for Vaayu (air), and Shraddhaa is the flower for Vishnu. Instruments are regarded as the flower for Vishnupad (means to attain Vishnu). By worshipping these 8 types of flowers Vishnu is pleased very soon.

Soorya, Agni, Braahman, cow, Vaishnav, heart, Vaayu, water, Prithvi, soul, and all living beings are the places of worshipping Bhagavaan. One should worship Hari in Soorya by three Vidya (Rig Ved, Yajur Ved, Saam Ved); in Agni by offering Aahuti of Havishya; in Braahman by felicitating him; in cows by feeding them with grass and water; in Vaishnav by treating them like brothers; in heart by meditation; in Vaayu by Praanaayaam; in water by offering flowers with water; in Prithvi, or Vedee or clay idol by reading Mantra, and all Bhog etc; in soul by treating all alike; and in all living beings by considering them all as the form of Bhagavaan. It is appropriate to worship Hari's Chaturbhuj Roop in all these places.
[Padm Puraan, 4/19]

In Padm Puraan, 4/17, Shiv Jee says to Paarvatee Jee - "Bhagavaan's worship is said to be of five types - Abhigaman, Upaadaan, Yog, Swaadhyaaya (self-study), and Ijyaa. Cleaning Bhagavaan's place is called "Abhigaman". Gathering flowers and sandalwood paste etc things is called "Upaadaan". My Isht Dev is not different from me - this feeling is called "Yog". To do Jap by understanding the meaning of one's Isht Dev's Mantra is called "Swaadhyaaya". Reading Sookt, or Stotra, doing Bhagavaan's Keertan, studying Shaastra etc also come under "Swaadhyaaya". To worship one's Isht Dev methodically is called "Ijyaa". They give Saarshti, Saameepya, Saalokya, Saayujya and Saaroopya named Mukti respectively."

In Padm Puraan, 4/19, Naarad Jee says to king Ambareesh - "Learned man should worship Hari by putting Havishya in Agni (fire), by flowers in water, by meditating in mind, and by Jap in solar system.

Some Animal Products Used in Poojaa
There are several products of animals which are used in Poojaa, like Naag Mani, Gaj Mani etc (how these animal Mani are treated as gems.), Vallampuree Shankh (conch).

In the most famous Tirumalaa Baalaa Jee Temple, they use the secretion of a species of a cat to apply to the Baalaa Jee idol.

Baalaa Jee's idol is applied with Civet (Punogu), as well as Kastooree (Deer Musk) and Ambergris (whale's mouth secretion, also I believe its the Teemaa Muktaa/whale pearl, or called Temegalam Ratnam in Tamil, Telegu, Keral languages) mixture with Real Mineral Cinnabar (Jadi Lingam) and Made made Cinnabar -Vermillion) in his Namam (sacred mark on his forehead). This practice is not unique to Baalaa Jee, but also done in Tanjore and Madurai for Shakti manifestation and in Maduraa for Shree Krishn. For Shakti Alankaar (decoration), Civet as eye brows lining, Kastooree (musk) and Ambar (ambergris) mixture as Tilak (Kastooree Tilak).
[From Sacred Objects Group, Apr 15, 2009]

In our scriptures, it is said that during the process of creation from the Supreme Brahm, the Space (Aakaash) came first and sound is the
property of the Aakaash. From Space came Air (Vaayu), and from Air came Fire (Agni), from Fire came Water (Jal) and from Water came Earth (Prithvi). Sound is an abstraction that is closest to the Supreme Brahm.

We employ different means to worship the Supreme Brahm. We worship It as a deity in the form of Earth, in the form of Water (in a Kalash), in
the form of fire (during Havan), in the form of air (through Praanaayaam etc) and in the form of sound (through the chanting of the Ved, and
chanting of the Divine Names).

However, in order to render an ideal fit for worship, Mantra (the form of sound) have to be chanted. In order to worship the Lord in a Kalash (vessel of water), Mantra are to be chanted to install the Lord in the Water. In order to worship the Lord in the form of Fire through Havan, Mantra have to be chanted to install the Lord in Agni. In order to worship the Lord through Praanaayaam, one should contemplate on and chant the Pranav Mantra. Thus all these forms of worship are rendered futile unless accompanied by the sound aspect in the form of Mantra.

However, if we were to worship the Supreme Brahm in the form of sound, mere chanting of the Ved or chanting the Divine Name of Lord alone is
enough. It does not expect any other accessory to make it complete. That is the greatness of worship by chanting the Divine Names.

Upon the dedication of oneself to ascetic, The Devtaa and Rishi should be worshipped in the East, the paternal ancestors in the South and the maternal ancestors in the West.
[Mahaanirvaan Tantra, p 185]