I work at a specialty running store where I provide gait analyses as well as consultation on training and nutrition. The majority of people that shop with us are first-time runners and walkers. Here are some tips to keep you running:
1. Don't go 0-60. If you run 15 miles one week, don't run 24 the next week. A good rule of thumb is to increase your weekly mileage by no more than 10% per week.
2, Get good shoes, and replace them when needed. Big-box stores like Dick's or Modell's have good selections, but if you can, find the specialty running store closest to you and get a gait analysis. Many common running injuries can be avoided by being fit for the proper shoe for your running gait. Try and replace your shoes every 350-500 miles.
3. Don't be afraid to sign up for a race. Committing to a local road race gives you a goal and a reason to train. Don't worry about your pace, running isn't what it was years ago. The running population has exploded and walker/runners of ALL ability levels are participating in races.
4. Don't run through an injury. Taking a few days off to recover is much better than sidelining yourself for a couple weeks because of stubbornness. A few days won't disrupt your training. A few weeks will. Rule of thumb: If the pain/soreness makes you change the way you run, then don't run.
5. Do something else. In the beginning you will improve by leaps and bounds, but everyone plateaus. A good way to get past a stagnation in improvement is to do something else. Cut down the running to a few days a week and hit the gym, jump on the bike, or swim some laps. This sort of cross-training will help strengthen the supporting muscle groups, making you faster and less susceptible to injury.
These tips originated in an interview with Gracie Ofslager