If you want healthy shoulders, your thoracic spine must have a good level of movement. Many people think their shoulders are tight so they go on a crusade of shoulder stretches to increase their mobility. But that's ultimately creating another list of problems, including instability and weakness.
If you struggle with getting a good overhead position in certain lifts, or can't achieve optimal bar placement for back squats, then your thoracic spine could be the issue. Improving your thoracic rotation is a great way to increase your thoracic extension.
Adding this drill to all of your warm-ups is a great way to consistently work on your upper back mobility.

Frog Thoracic Rotations

Here's how to do it:
  1. From an all-fours position, go wide with your legs so that your point of contact with the floor is the inside of your knees.
  2. Move your hips back and lock them into place. They shouldn't move from this position during the drill.
  3. Bring both elbows down to the floor and brace your abs as if you were performing a plank.
  4. Lift one arm up until it's at a right angle with your thumb pointed backwards. Keep your shoulder blade pinned down flat.
  5. Squeeze your fist as hard as you can and maintain tension throughout your shoulder.
  6. Start to rotate through your upper back. You should feel your ribcage being opened up and like you're "pulling" with your back muscles.
  7. Go as far as you can and pause for a few seconds as you take a deep breath in, then exhale and return to the start position.
  8. Repeat for 3 sets of 5 reps each side, slow and controlled.
Make sure to use an exercise you're struggling with as a test, like the back squat, overhead squat, or overhead press. Do the exercise a few times, complete a full set of frog thoracic rotations, and then retry your test exercise. You'll notice a difference!