There are different ways to train, and having a coach is probably the best way to get where you want to be in a safe and sure way. For beginners who don't have a coach here are some tips I have learned through my own experience.
1. Structure your training - to get the proper recovery and consistency to avoid injuries - if you are training for less than 5 days a week it's better to spread your workouts than bunch them in consecutive days
2. Run at an easy pace - develop aerobic system and avoid injury by not putting too much stress on your body - 60 to 75 percent of your 5K max
3. Get a hard and fast workout every 10 days to strengthen the muscles you needed to run fast - examples: 4K max workout, or a 10 x 400 meter run
4. Swim - to develop your cardio without putting added stress on your lower body
5. Mind your weight - to avoid injuries from running at a heavy weight - avoid soda and junk foods
6. Gear and apparel - training shoes should be comfortable and with enough cushion to protect your feet and knees, hydration gear is a must for instant access whenever needed
If you don't have injuries you can also have one like this