There are many different ways to deal with clogged sinks. You can plunge, pour boiling water down the drain, use baking soda, and so forth. Having to try three or four different approaches before you find one that works can be frustrating. A better approach is often to first identify what is most likely causing the clog so you can start with the most effective solution for that particular type of clog.
Hair Clogs (Common in Bathrooms)
If the clog is in the tub or in a bathroom sink where you often wash your hair, shave, or bathe a pet, chances are good that hair is mostly to blame. Even a thin layer of soap scum or mold inside the drain can start grabbing onto hair. Then, more hair gets caught in that hair, and the clog gets worse and worse.
The best way to remove a hair clog is usually physically. Start by sending a small plumbing snake down the drain. (This is a long, metal device you can buy at the hardware store.) Rotate the snake as you send it down the drain. With any luck, it will be long enough to reach the clog; you'll feel resistance when it does. Pull the snake back out, and the hair ball should be attached to it. Then, pour some white vinegar down the drain to get rid of the soap scum that attracted the hair in the first place.
Grease and Food Debris Clogs (Common in Kitchens)
In kitchen drains, it's common for a little grease to cling to the inside of the drain. It solidifies when exposed to the colder drain pipes. Then, it grabs onto food debris as it travels down the drain, and the clog grows larger. It's hard to physically remove this type of clog since it's not one solid piece. Instead, your goal is to break it down and rinse it all of the way down the drain.
Start by pouring a big pot of boiling water down the drain. Be very generous. The heat will "melt" the grease that's holding the clog to the inside of the pipe surface, allowing it to slide down. Once the water starts moving down the drain more freely, follow up by pouring a few cups of baking soda and a few cups of vinegar down the drain. Let it sit for an hour; the foaming action will help loosen any remaining grime.
If you've tried everything and the clog persists, talk to a plumber like those at AAA Plumbing for more help.