Question: How to fix a chair that has become wobbly.
Option 0: You will need furniture glue for the best result. Glue the joints and places where pieces meet, such as the tops of the legs or where slats are placed in the chairback. Glue these spots to strengthen the chair. Let the glue dry overnight before anyone sits on it to ensure the glue is  set properly.
Option 1: You will need furniture glue for the best result. Sand down the joints and places where pieces meet, such as the tops of the legs or the slats in the chairback. Ensure these are smoothly sanded and there are no splinters or rough edges before anyone sits on it to ensure the chair pieces are set properly.
Answer: 0