Summarize the following:
Lie on your back, with your legs bent to about 90 degrees at the knee and your feet on the floor. Pull your bellybutton up towards your chest and hold it for 10 seconds.  Your core muscles are essential to support your posture, so the more you can work them, the better your posture will be. Repeat 8 times, and practice it daily. Breathe normally during this exercise, as you are training your core to be able to maintain this position during normal activities in daily life. While sitting in a chair, sit up straight and squeeze your shoulder blades together. Hold for a count of 5, and then release. Repeat this 3 or 4 times daily. Exercises that strengthen the muscles across your upper back and shoulders help you maintain good posture. Try the following strength exercise, with or without hand weights:  Start by squaring your posture. Extend both arms straight out in front of you with your palms up. Bend your forearms toward your shoulders, trying to touch your shoulder blades with your fingertips. Do 10 repetitions with both arms, then alternate 10 reps for each arm by itself. While you wait for a web page to load or the bread to toast, place your elbows at your side, and touch your shoulders with your hands, creating your "penguin wings." Keeping your hands on your shoulders and your ears aligned, raise both elbows (count 1, 2) and lower them back down (count 1, 2). Do as many reps as your wait allows. You'll be surprised how many stretches fit into 30 seconds. Tilt or stretch your head in all 4 directions over your shoulders (forward, back, left, right), and gently massage your neck. Avoid rolling your head in a circle, as it may cause further strain.  For another exercise, get on your hands and knees. Curl your back upwards, like a cat, and then do the opposite, dropping your stomach down and curling your back downwards. Repeat the exercises a few times each day. Doing them in the morning helps your body stretch out the muscle lethargy from sleep. Doing periodically throughout the day will help to raise your energy level. Yoga is excellent for posture and for your health in general. It can also improve your balance. Yoga works your core muscles, making them stronger and helping you to keep a proper body alignment. Yoga will also help by teaching you how to hold an erect posture while sitting, standing, and walking. Look for classes in your area, or scout YouTube for instructional videos.

Summary:
Improve your core muscles with deep abdominal stretching. Do a shoulder blade squeeze. Train your muscles for better posture with strength training. Pretend you're a penguin to stretch your shoulders. Use stretching for a sore neck or back. Practice yoga to increase flexibility and help with posture.