There are 2 types of plungers: a “cup” or flat bottomed type that is used for sinks or a “flanged” or tapered plunger for toilets.
Make sure you are using the right plunger for the job. Knowing how to use a plunger correctly means you won’t end up with an injury. Also, the suction could be ineffective to remove a clog.
For a toilet clog make sure the tapered end of the plunger is placed completely over the opening at the bottom on the bowl to create the suction needed. When you compress the plunger, it should be evident that it has made a good contact with the drain at the bottom. There will be some resistance when you pull it back.
Use short, quick straight in and out motions with the plunger. Don’t let your hands slip on the plunger arm, as it could cause an injury. After several tries, if you are not able to clear the toilet, you should call a licensed professional. They have the expertise to clear the toilet without causing any damage to the porcelain.
If you wish to try to unclog a sink, use the flat bottomed plunger. You will also need to plug up the overflow drain opening in the sink or tub. This will help create the suction needed to loosen a clog. Again, make sure the bell of the plunger is completely covering the drain and with short, rapid up and down movements, try to loosen the clog. If the clog is not released after a few tries, you will probably need the services of a plumber.
Note: If you have put chemical drain cleaner in the sink, be sure to wear rubber gloves to protect your skin from any splash back.