Dumping used cooking grease down the drain can clog your pipes: It may be liquid when you pour it, but it will cool and harden quickly. "Even if it doesn't mess up your pipes, [everybody's plumbing] dumps into the city pipes and the grease builds up, eventually causing a blockage, which leads to sewer spills," says Donna Souza, the program manager of the Food Establishment Wastewater Discharge Program in San Diego, California. The best way to dispose of grease is to keep it out of the plumbing system entirely by reusing it or recycling it.
If you have some high-quality grease you actually want to keep, say, rendered duck fat or highfalutin-bacon grease, let it cool down a little and strain it into a jar, then store it in the refrigerator. You can use it to roast potatoes or start an unending cycle of greasy bacon-frying (see video below). If it's a large quantity of oil from deep-frying, you can cool it down, store it, and use it again. But beware of what you've fried in it: Flavors linger. Don't fry doughnuts in oil you've already used to fry seafood.
If you don't want to reuse your grease or cooking oil, just cool and collect it in an old container for recycling: Many city recycling facilities, from Columbia, South Carolina, to San Diego, California, are starting to accept it from residential homes. If your city doesn't, Souza says the grease or oil should be poured into an unrecyclable container and thrown in the garbage.