Fartlek is a Swedish word for speed play. It's like an unstructured speed workout. It's great for beginners because there's no determined distances that you have to do. You don't have to start with 1/2 mile repeats. You don't have to start with a full loop around the track repeats. You can be anywhere you are with your run and you can start your increased speed, maybe you want to work until the next lamppost, maybe you want to work until the next house, or maybe you want to work on to the next tree, but you're slowly increasing your speed and then you're taking a rest for about that same amount of distance. You can do as many repeats as you want.
We recommend you start slow, maybe two to four, but at least once a week to help you increase your speed. Fartlek workouts will help you run a little bit faster in the long run because you're challenging a different system of your body, and those longer runs your doing at that slower speed will start to become a little bit easier over time, as long as you're using that Fartlek workout at least once a week.
Hill training is a great way to help you run faster. Find a hill in your area or maybe if you don't have hills in your area you can use a treadmill with an incline on it. So what you're doing is that you're using that hill for a specific distance or a specific time. Maybe you want to start at 30 seconds, 60, seconds, or even 90 seconds. What you're doing is your challenging up that hill at an increased speed for about that same amount of time, the 30, 60, 90 seconds and you're jogging back down that hill for a recovery.
So again, if you're going to use hill training as strength training or to help you increase your speed, you want to do that at least once a week, and each week add at least one or two more repeats to help you challenge yourself as you go along. If you're looking for ways to increase your speed or to become a stronger runner Fartlek training and hill repeats are ways to do it.