They worship God by: telling His story, narration of His influence, virtues, greatness, character, etc. in the presence of other devotees, chanting of his names - Ram, Krishna, Govind, Hari, Narayana, Vasudev, Keshav, Madhav, Shiva, etc. - and singing devotional songs, singing his praises in a loud or mellow voice, sitting or standing, with music and dance or without, reciting divine hymns and beautiful odes dedicated to Him or in any other way praising him.
Devotees pay their obeisance to God by bowing to Him with whole-hearted faith and devotion: at the temple, in front of the picture/idol of him at home, through his names, by touching his feet/sandals, in the form of religious scriptures which highlight the essence of God and relate stories that describe his love and influence, by thinking that God resides in every being.
On the other hand, thereis another kind of devotee who believe in the "brahma". They worship their form-less (niraakaar) God by: not neither taking pride in being the doer of any work nor expecting any fruit of the labor, condiering the world is ephimeral, believing that none is greater than the supreme "brahma" and continually practicing to stay in that state through meditation, etc.