Do 3 main exercises each week in order to increase pace:
- Do repetitions of about 3 * 400m at 90% of capacity with 2 minutes off once a week. This should feel hard, and it's ok if you cannot do 3 to begin with. None of your other runs should come close to the difficulty of this. Do this twice a week.
- Do one "long run" a week, where you try to run, without stopping, for a given length of time. This run should be at no more than 70% of your max HR. The idea of this run is to build endurance, and to concentrate on style; often in faster runs under pressure, style deterioates into old habits. Run for however long you can run for now without stopping, and without feeling completely exhausted by the end and gradually increase the time each week, up to about 1:20 minutes.
- Do a timed "fast" medium distance run. This is a run where you do 4kms at a pace that is just above combfortable talking. Begin this by a 20 minute slow warm up jog. Do this once a week.
Remember also, take it easy! If you show your body samples of what you want it to be doing, growth hormone will naturally do it's work at night time. Beginners can sometimes be over-enthusiastic and if there is any "twitchiness" or soreness while running, stop that day's exercise and rest.
Each exercise should be done to the extent that you feel that you have had a workout, but with enough left in reserve so you feel like doing it tomorrow or the day after. If you do any more you might burn out. Regularity before intensity!