Bathroom and kitchen sinks will inevitably clog. Over time objects such as food, hair, and dirt will build-up and settle in the trap or somewhere else along the line and you’ll notice your sink draining much slower.
Before your sink completely backs up, take this as a warning and clean out the trap (the U-shaped pipe under the sink). Some traps have a clean-out plug that can be opened with a wrench and allow you to get to the blockage without removing the entire trap. But if you do have to take out the trap its an easy process with the use of a towel and wrench. Remove the slip nut at each end and remove the trap then remove any blockage and replace the trap. If the trap is clear you may need to use an auger or snake to clear any blockage further into the pipe.
It’s advisable to clean the trap before you the sink completely clogs and it’s not always wise to rush to the plunger as that can push a clog further into the pipe and make it more difficult to clear.