When thinking about posture exercises you need to work your body opposing gravity. Gravity will pull your shoulders down and make you slouch. You need to regain your posture. Here is one exercise to help regain proper posture.
Stand with your back against the wall; Put your heals, hips, shoulders, and head flat against the wall. This may feel unnatural, but this position is proper posture. Then bring your arms up against the wall forming a "goal post". Your elbows, wrists, and fingers are all flat against the wall too. Now, keeping both arms, elbows, wrists, and fingers on the wall, straighten your arms above your head as much as you can without losing contact with the wall. Then bring your arms back down to the "goal post" position without losing contact with the wall ever. This is one repetition. Do 3 sets of 5-10 repetitions a day. For more information, visit my website at www.hermenhealth.com.