The Latin term ritus means means a rite that is performed in the customary and usual Roman manner (Festus s. v.). More specifically ritus refers to a Roman rite where prayers are correctly spoken, and the customary gestures and actions of Roman ritual are used. It is a marriage of prayer and action where the words giving meaning to an action and the action gives substance to the words. Furthermore a Roman ritus can be said to be composed of four parts:
I The Approach
II The Gesture and Prayer
III The Request
IV The Reply
One ought to know which God or Goddess he is calling upon, what are appropriate offerings to bring for the deity, how to address a particular God or Goddess, when and where to perform the ritual and other considerations. This can be a little complicated in any polytheistic tradition, but there is always a certain internal logic in a tradition that aids a worshiper when approaching a God. In the Roman tradition there is even a traditional manner of approach when you do not know what God or Goddess might be present in a place. The prayer and gesture is generally specific to the kind of rite being performed, where as a request may be more specific to the occasion or desire. Not always, but during a formal Roman rite one also takes a moment to see whether any sign appears to indicate whether one's offerings have been accepted or reject in reply to your request. This sounds more complicated than it actually is in practice.
A relatively simple rite is called the adoratio. It may involve a simple greeting such as saying "Ave, Ave, Di parenti." This greeting is coupled with a gesture where in one kisses the back of the right hand just behind the knuckle of the index finger, and then touches the finger tips onto an altar or an image. It is specifically used when addressing one's ancestors, so one approaches a family member's tomb, or the family lararium within the home, or sometimes it might be a tree or other outdoor shrine. The adoratio was so closely associated with rites for deceased family members, that is could be used interchangeably for the annual ritual owed to the dead in a parentatio. An adoratio can also be used with certain celestial deities when They are approached in a parental way. One example from Roman literature is where a woman would stop by each shrine and image of Venus, calling upon the Goddess to lend her daughter beauty and poise. In word and action the mother both promised Venus sacrifices in the future while reminding Her of past sacrifices, while at the same time she was including Venus as a parental figure to her daughter and thereby asked Venus to take a special interest in the welfare of her daughter.
More at Patheoshttp://www.patheos.com/blogs/religioromana/2012/01/rites-rituals-and-ceremonies/