World class runners usually run with a stride rate of about 180 steps per minute (counting the steps made by both feet). Some authors in discussing this refer to cadence which is the number of steps per minute taken by one foot.
I have learned from my own experience that running with a stride rate about 180 is a good technique. Running at that rate trains my body for quick leg movement and thus makes me a stronger runner. In addition, if I come to a hill or encounter a strong head wind, I can slow my stride rate without danger of my running changing into walking (of course, if I desire to walk, I can slow to that pace).
Increasing the length of ones stride can cause injury if it is done improperly. Dr. Gabe Mirkin suggests that one not intentionally increase his or her stride length. Instead he suggests that we train to develop stronger leg muscles that will drive us forward with a longer stride. Read his articles to get the details of his suggestions.
I've found his suggestion to be good. As I do speed workouts, I've noticed that I not only increase my stride rate, I also increase my stride length. I don't intentionally try to increase my stride length. The increase automatically happens as a result of my workouts. I read an interesting article that explained that if you consciously try to increase stride length, you risk having your heel hit in front of your knee, and that is the road to injury.
I recommend that runners learn to run with a stride rate about 180. For many runners, this will be a rate that is faster than their normal running rate, and they will have to train their body to slowly increase to a value near 180. That is, to increase their stride rate, they will have to do speed training, and I recommend they delay that until they have increased their distance to a point where they can level off in distance and then focus on increasing their stride rate. My page on speed gives suggestions for speed training.
In addition, don't intentionally try to lengthen your stride. Let your body find the stride-length that is appropriate for your body. Your stride-length will automatically increase as you become a stronger runner.