1/2 cup baking soda
1/2 cup vinegar
Pour baking soda down the drain and follow with vinegar. Cover and let sit for at least 30 minutes. Flush with boiling water.
Tip: Prevent the shower from clogging by using a drain trap to catch hairs.
Personal Note: I just finished doing this in my master bathroom sink and it works like a charm! No chemicals needed and the cost was a fraction of what it would have been if I purchased chemical drain opener. Win-win.