Run in a group if able. You'll want to best each other and won't notice that you're pushing yourself. Try to find people at your speed and endurance for this. Meet regularly with this group.
Vary your workout. One day, do hills. The next day, do a really long run. Another day, do sprints. This helps you improve every aspect of running and makes it more transferable to other sports/activities if that's a concern.
Get some good stretching in. Try to do a warmup before stretching; this reduces the chance of straining something during the stretching. Also, try to do some dynamic stretches (such as running 100m, each step bringing your thigh high enough to be horizontal).
Listen to your body. If you're working yourself really hard, go for something lighter to regain some energy.
Try to run every day. It helps.
Try to avoid stopping in the middle if possible; it kills your mental momentum.
Then there's the stuff that applies to everything, like always staying hydrated.
Lastly, a general tip for running: speed is generally proportional to the number of strides, not the length of them. Focus on improving the former, not the latter.