How do I organize a paragraph?

Narration: Tell a story. Go chronologically, from start to finish.
One North Carolina man found quite a surprise last year while fishing in the Catawba River: a piranha. Jerry Melton, of Gastonia, reeled in a one pound, four ounce fish with an unusual bite. Melton could not identify it, but a nearby fisherman did. Melton at first could not believe he had caught a piranha. He said, “That ain’t no piranha. They ain’t got piranha around here.” Melton was right: the fish is native to South America, and North Carolina prohibits owning the fish as a pet or introducing the species to local waterways. The sharp-toothed, carnivorous fish likely found itself in the Catawba River when its illegal owner released the fish after growing tired of it. Wildlife officials hope that the piranha was the only of its kind in the river, but locals are thinking twice before they wade in the water.

Description: Provide specific details about what something looks, smells, tastes, sounds, or feels like. Organize spatially, in order of appearance, or by topic.
Piranha are omnivorous, freshwater fish, which are mostly known for their single row of sharp, triangular teeth in both jaws. Piranhas’ teeth come together in a scissor-like bite and are used for puncture and tearing. Baby piranha are small, about the size of a thumbnail, but full-grown piranha grow up to about 6-10 inches, and some individual fish up to 2 feet long have been found. The many species of piranha vary in color, though most are either silvery with an orange underbelly and throat or almost entirely black.

Process: Explain how something works, step by step. Perhaps follow a sequence—first, second, third.
You can safely swim with piranhas, but it’s important to know how and when to do it. First, chose an appropriate time, preferably at night and during the rainy season. Avoid piranha-infested waters during the dry season, when food supplies are low and piranhas are more desperate. Piranhas feed during the day, so night-time swimming is much safer. Second, streamline your movement. Wild or erratic activity attracts the attention of piranhas. Swim slowly and smoothly. Finally, never enter the water with an open wound or raw meat. Piranhas attack larger animals only when they are wounded. The presence of blood in the water may tempt the fish to attack. If you follow these simple precautions, you will have little to fear.

Classification: Separate into groups or explain the various parts of a topic.
Piranhas comprise more than 30-60 species of fish, depending on whom you ask. The many species fall into four genera: Pygocentrus, Pygopristis, Serrasalmus, and Pristobrycon. Piranha in the Pygocentrus genus are the most common variety, the kind you might find in a pet store. Pygopristis piranha are herbivores, feasting on seeds and fruits, not flesh. In contrast, fish in the Serrasalmus genus eat only meat, and their teeth are razor-sharp. Pristobrycon are the least friendly of all piranhas; they often bite the fins of other fish, even fish of the same species. The label piranha, then, refers to a wide variety of species.