Three groups of prepositions are identified: (1) prepositions of place, position and direction, (2) prepositions of time, and (3) prepositions for other relationships. The document then provides examples of common prepositions that fall into each of these three categories. It also discusses rules for using the prepositions "at", "in", and "on" with times and places. Specific examples are given to illustrate the uses of these prepositions.