I love hill workouts. I used to think that I was alone in this, but Bea Q. and the Ginger Amazon love them too, enough that we have a standing date to do hills together, once a week, before sunrise. 

Hills are such an efficient way to build power and stamina. There are two major kinds of hill workouts, intervals and repeats.

Intervals are a great place to start, especially if you are new to this kind of workout. Run a warm-up, then start your hills: 60sec up, 30 down, repeat until you're appropriately fatigued, and do a cool-down. As you get stronger, you'll be able to do more repeats before your fatigue point, and you can even start experimenting with longer or varied intervals. Intervals translate to awesome burst speed in flat conditions.

Repeats involve more sustained climbing: you go all the way up, then all the way down, running for distance rather than by your stopwatch. Because you are taking the whole hill at once, you may choose to strategically walk certain pitches, but you maintain uphill progress the entire time. I use repeats to train for longer adventures with lots of total vertical, or mountain and uphill races.

Just make sure you are listening to your body and using good form on your hill workouts. Don't rely on your toe-off to create power or you risk calf strains and Achilles problems. Get your butt and quads in on the act, and use those big muscles to climb! Also, use your downhills to recover. Downhill repeats are a distinct kind of workout with a different purpose, and you'll actually be less effective with your repeats without a full recovery cycle. Shred your uphills, but float back down.