First off start with a good foundation- sneakers. Always purchase your sneakers or shoes in the late afternoon or evening to ensure the best fit. As the day progresses the effect of gravity causes some swelling to occur in our feet. Shoes purchased earlier in the day will bind due to this natural swelling. Another thing is purchase shoes for the sport you are planning on joining as they are designed to provide the support needed. People with flat feet or those with high arches should make sure the padding inside properly supports their feet preventing the arches from collapsing or undue strain.
Secondly- gentle stretching. To aviod injury it is important to keep your muscles flexible. There has been some change of thought in when to perform stretching exercises, initially it was felt that stretching both prior to and after exercising was most beneficial but now more is being said for stretching after exercise when the muscles are warmed up to prevent them from being too lax during exercise. In any case I found some excellent stretching exercises on ehow: http://exercise.about.com/library/blbasicstretch.htm
During any stretching program be careful not to lock your knees in extension and only stretch to the point of resistance.
Thirdly-type of exercise. Weight bearing exercises such as running and jogging place alot of strain upon our bodies. Joint compression forces are magnified in these activities which may aggravate tender tissues. Pacing is also important, generally a slower pace will less likely cause muscles to have a quick stretch repsonse. Some exercises you can try:
- Walking- pay attention to the surface you walk on as well, soft surfaces such as sand provide increased difficulty. Walking through water also provides resistance the faster you walk and the deeper you go.
- Yoga- there are many different forms of Yoga that can be tried, in addition to flexibility Yoga can also improve balance and core strength.
- Tai Chi or Qi Gong- the fluid movements of these exercises help promote flexibility, balance, and flow of energy in the body.
- Cycling- this is generally easiser on the knees and can be done outdoors or indoors on an exercise bike. There are different types of exercise bikes out there as well and brands with different features. There are standard styles where you are sitting upright and recumbent models where you are leaning back which may be more appealing to some.
- Elliptical Machines-these combine the benefits of walking and cycling together which you may find easier on the body. (They were a personal favorite of mine to warm up with back when I had a membership in a gym.)
- Swimming or Water Aerobics- You can get a great workout in a pool. Water has properties that make it an excellent medium in which to exercise namely surface tension and buoyancy which provide resistance. Resistance can be increased using various floats and paddles. Heat is of particular note because of it's effects on the body increasing blood flow and reducing tension. The compression forces in water increase with depth which helps move fluids in the body (this is what causes the bathroom run when you get out of the pool).