First, remove maximum water accumulated in the sink. Use one cup of baking soda and throw it down the drain. Then pour enough quantity of boiling water down the drain. The sink will be empty within minutes. After this, pour more boiling water which will clean it thoroughly. Then flush it with cool water for few minutes.
Next method is to remove maximum water accumulated in the sink. Use one cup of baking soda and throw it down the drain. Then pour household vinegar down the drain and plug the drain using sink stopper for about half an hour. Then unplug the sink and pour boiling water on the top. If clogging still persists, double the quantity of baking soda and vinegar and leave if for one hour. After water in the sink drains fully, flush with boiling water two to three times to clean out the gunk.
After following above methods, if you find the sink full again, check the drain trap for any accumulating mass which might be blocking the drain. If it is not blocked, then you can try drain flushing throughout the day. If you are using double sink, you should make sure that you insert drain stopper on one side and work on the other. While using chemicals to clear the drain, you must be careful so as not to harm yourself in any way. It is advisable to wear eye protective gear and not to remove the drain trap since the water filled with chemical may get splashed on your face.
There are three types of chemicals used to clean the drain and they are caustic, acid, and enzyme. The caustic chemicals act powerfully on grease and oily matter. Acid is very effective in removing soap and hair and also it works faster as compared to caustic acid. Enzymes help in cleaning the drain as they consume organic materials. This is safer than caustic and acid, but acts slowly. All these three are a must in a household and according to the types of clogging, one of these should be used. It is wiser to keep these products away from children and pets.
Last but not the least, all the members of the family must have some kind of training and knowledge about drain clogging. They must see to it that food particles, cloths or any other material does not go into the drain.