Let’s find out what Hindu scriptures say about it.
Unluckily at this time Lord Shiva came back. The Parvati’s boy denied him to enter in. Lord Shiva introduced himself as the consort of Parvati, but that boy again denied his entry. Lord Shiva became so annoyed that he had taken out his trident and beheaded him. Goddess Parvati had taken her bath and on her return she witnessed her son’s beheaded body. She became enraged and vowed that he would devastate the world if her son would not survive. Then Lord Shiva replaced Parvati’s son head with an elephant’s head and gave him life. When Goddess Parvati saw her son with the head of an elephant, she was enormously unhappy. Lord Shiva pacified her and baptized Parvati’s son as Ganesha and blessed him with divine powers and affirmed that no prayer or auspicious work would never get completed without invoking Lord Ganesha's name and blessings. Hence, Lord Ganesha was worshiped first and given name 'Pratham pujya'.
According to Shiv puran, once there was a fight between Gods that who amongst them would be the best. All of them came to Lord Shiva for the suggestion. Lord Shiva advised them that all of them would participate in race competition by circling the world. The one who would return first would be acknowledged as the winner and would be worshiped first. KartikeyaKartikeya
Kartikeya is the son of Shiva and Parvatiand is regarded as the commander- in-chief the army of the gods. Being the son of the supreme couple
, the elder brother of Ganesha joyfully get started on his peacock, and similarly other God were ready on their vehicle to circle the world. Ganesha was sharp minded, circled around his parents because he considered his parents were the Universe. As a result, Ganesha was acknowledged as the conqueror and hence Lord Ganesha is prayed first.
According to a yogic viewpoint, every day we perform either material or spiritual actions (Karmas). Yogis believe that there exists series of minor and major energy centers called chakras in human body, and they are mainly:
Root Chakra (Muladhara),
Sacral Chakra (Swadishthana),
Navel Chakra (Manipura), Heart Chakra (Anahata),
Throat Chakra (Vishuddha),
Third Eye Chakra (Ajna)
Crown Chakra (Shasasrara).
Yogis believe that Lord Ganesha rules the 'muladhara chakra' of our body. This particular chakra is the interface between the material and the spiritual worlds.
Lord Ganesha is said to control both these worlds. He is the one who fulfill our worldly desires without any obstacles in this world while progressing on our spiritual journey towards the goal of achieving salvation. Thus, people worship Lord Ganesha before beginning of any important work whether it is of materialism or spiritualism.