Hi Therese I would start with a cup of baking soda followed by several cups of bowling water. If that doesn't work you might consider moving on to harder core products like Draino
dump baking soda in drain,add white vinegar (gonna fizz) then add boiling water alot to flush out drain may need to do this first;use needle nose pliers or coat hanger to get in drain opening & pull up wads of hair yeah it's gross. may need to let baking soda vinegar sit in drain over night then rinse well with boiling water in morning
Remove drain cover. Use a drain cleaning tool to remove any items that are clogging the drain like hair. You can buy a plastic one for just a couple of bucks.
If you still have clogged issues: add 1 cup baking soda and 1 cup white vinegar. Cover drain opening to keep the effervescent effect in the drain as much as possible.
Boil water and after 20 minutes pour the boiling water down the drain.
Cover the overflow hole with wet paper towels. Pour some baking soda down the drain. Then pour down some vinegar. Immediately cover the drain with a cloth and press down. The foaming will force the clod through.