Here is the method I use for binding. There are a few details that help with the corners. Pay attention to the corner folds. You want them at a 45 degree. Work the binding until the corner is good. Fold one side up and one side down to prevent bulk in the corners.
https://www.youtube.com/watch?v=dQgjp4Upt8w
You also want to start with square corners on the quilt.
Another helpful one.
https://www.youtube.com/watch?v=rjShcNgYk0E
I have even used a small ruler and marked the stitching line right on the binding to help with the corners. Stop stitching 1/4 inch before the corner.
Good Luck!