If you've never run before, here are some Beginner's Tips for non-runners from the runningday.org site:
It’s easy to get started running. Here are some simple guidelines everyone can follow to safely and pleasurably develop their ability to run.
Relax. Running is a natural act, like breathing or walking. Just about anyone can do it. It is, however, recommended that you consult a health professional before undertaking a serious training program. You may wish to start by walking first, and then gradually incorporating running into your training program.
Think positively. Don’t be discouraged. If you can get through the first several weeks of training, you will find that what seems like a big effort at the start will soon feel natural and easy to you. Within a few weeks, you will experience the pure joy of running down the street or along a park path.
Buy quality gear. The only equipment you will need is comfortable exercise clothes and good running shoes. Go to a running specialty store and get advice about the right shoes for you. You can get good running shoes for $80-120.
Train with a plan. Choose a running/walking course that is readily accessible to you. During your first two training weeks, try to run two or three times per week, on alternate days. When you feel ready, increase to four days a week, then five days. The idea is to build up gradually. Even top competitive runners take days off regularly to rest and avoid injury. Stretch your muscles on both your running and non-running days.
It’s okay to walk. Begin your first workouts with 15 minutes of alternating walking and jogging: Walk for five minutes, then run easily for two or three minutes; repeat. If you are comfortable jogging from the start, that’s fine, but do not run the entire time even if you think you can. Don’t worry about the distance you cover. On your third or fourth workout, try increasing your time to 20 minutes. After three or four more workouts, move to 25 minutes, then after another three or four workouts, try a 30-minute continuous run. Don’t force yourself to go farther or faster than what feels comfortable to you. The idea is to keep running regularly, and you’re more likely to do that if you’re enjoying yourself and looking forward to your next run.
Run at “conversation” pace. If you can’t chat with your running companions, you are going too fast. If you are running alone, try singing to yourself, out loud, to make sure your effort and breathing are under control. If you can’t sing, slow down.
If your schedule allows, include cross training. Biking, elliptical training, and lifting light weights can help strengthen non-running muscles and prevent injury. Swimming and deep water running can also be helpful in balancing your training and avoiding injuries.
Aim for a race. Pick an event that’s at least six weeks in the future. An ideal distance for your first race would be 5K (3.1 miles) or four miles. This is short enough so that you can truly be ready for your first effort, and long enough to give you the sense of accomplishment that will fuel your future running. Your goal should be to finish, enjoy the event, and look ahead. Start at the back of the pack, hold yourself back at the start, and run within your comfort range. If your time was slow, that’s good—now you have a base from which to improve.
For your next race, try a few short speed workouts. After a mile warm-up, run a series of faster intervals with jogging in between. A good “starter” workout is a sequence of about 400 meters at a quicker pace, followed by a slow 400-meter jog, repeated six times. This will loosen up your legs, lengthen your stride, and give you the confidence you will need to race.