29 Ellipsis
Only use evidence which is necessary to illustrate the point you are making. When eliminating unnecessary information, use ellipsis to indicate you are leaving part of the quotation out.

Excessive quotation: Criticising the Cyclopes for their lack of political organization, Odysseus noted that "... these people have no institutions, no meetings for counsels; rather they make their habitations in caverns hollowed among the peaks of the high mountains, and each one is the law for his own wives and children, and cares nothing about the others ..." (Odyssey, 140)

Revised sample: Criticising the Cyclopes for their lack of political organization, Odysseus noted that "these people have no institutions, no meetings for counsels; . . . and each one is the law for his own wives and children" (Odyssey, 140)

Note: You don't need ellipsis before and after a quotation, since it's clear you're omitting material at either end of the quotation.