Here is a core strengthening sequence you can do right from your home. The core center is so important - we use our abs for nearly everything we do (which I learned the hard way when I got an ab injury over the summer!). It's what supports us when we are doing even the most basic stuff like sitting or standing, so strengthening the core helps with posture, and can help prevent low back issues.
Tips for this sequence: Try to breathe 3-7 full deep breaths in each posture. Keep the hips lifted away from the ground when you're in side planks. If you're weak in the core, try the plank and side plank part of this sequence on your knees. When you come to the 12th and 14th pictures, make sure your shoulders are over the wrists and you are squeezing the abs as you pull the knee in towards your forehead.