If you cite one source in a few sentences in a row, you can put the citation only after the last sentence.
example : Each year, at least 7.8 trillion gallons of water are drawn up from the Ogallala Aquifer to irrigate the crops planted on the High Plains. These crops are the main food source for our entire country. Tragically, irrigation is depleting the aquifer faster than it can replenish itself, and that is the problem. In fact, only the tiniest fraction of the water is ever replaced in the Ogallala Aquifer. If the water were ever fully depleted, the aquifer would need 6,000 years to refill naturally (Zwingle 83).
After you quote, put the citation, even if the next sentence's info comes from the same source
example : The "court upheld the water company's right to capture water under its property and bottle it" (Patoski 185). Other organizations, including corporate giant Alcoa, plan to mine the water from their land and sell it to cities like El Paso (Patoski 185).
Put a citation at the end of each sentence if the page number from your source changes (that is, the two sentences have the same source but different page numbers)
example : According to one historian, Medieval teenagers chose entertainment that helped improve their standing with the other sex (Cooper 158). Being a good shot with a crossbow was an admirable skill 500 years ago (Cooper 159).
Some websites have no page numbers, so just skip that part
example : One account reports that "in the 1580's the most popular sytle among teenagers in France was striped pants and checked shirts for boys, along with dresses trimmed in brightly colored ribbons for the girls" (Brown).
Some sources have no author, so substitute the first part of that source's works cited entry (usually the article's title)
example : One account reports that "in the 1580's the most popular sytle among teenagers in France was striped pants and checked shirts for boys, along with dresses trimmed in brightly colored ribbons for the girls" ("Teenage Style" 324).