Beginners Exercise - Body Weight Squats
This is absolutely the BEST exercise you can learn to do and should be a part of your regular exercise routine. I talk about them a lot but you NEED to be doing these. If you have knee trouble, first make sure you are getting your but out far enough as you should not feel it in your knees. Make sure you are pushing down through your heals not your toes. Its awkward at first. Keep your back straight. If you still feel it in your knees get a kitchen chair to put in front of you to hold on to just to stabilize, do not use your arms to pull you up!
Here is a good video that demonstrates the technique: