Don’t slump. Stand straight. If you slump it exaggerates the curve of your spine, puts a load on parts that aren’t meant to carry that load your lower back and makes you look frumpy. Stand comfortably with spine straight. Keep shifting your weight from foot to foot to distribute it evenly.
Try and sit straight, but don’t sit very rigid like the women of the Victorian times. Be natural with relaxed shoulders. A small soft pillow at the base of your spine does wonders. You can keep your feet on a foot stool.
Straighten your lower spine. Lift and stick out your chest that squares the shoulders and keeps them in right place. Now when you walk you will find it much easier and so right.
Exercises that you can do to keep your posture correct is place a book on your head and walk slowly from one end of the room to the other without dropping the book or letting it slide. This not only gives you the carriage of a queen, but it also enhances your blood circulation to all cells in your head and neck, reduces tension and improves breathing and thinking.
Stand sideways in front of the mirror and look at your tummy. Now tighten the tummy. Probe it with your fingers to make sure it is hard. Next walk with a tight belly to the other end of the room. Do that three times a day. If you can walk for an hour with your tummy tucked in.