1) GHR's with weight for extra resistance (hold weight at chest)
2) GHR's with arms extended overhead.
Some key points:
1) Proper alignment matters - Your body should remain in a straight line from head to heels. Do not allow your hips or neck to sag, or your lower back to hyperextend. Also, there should be no rotation occurring in your pelvis, thorax, or spine.
2) Lock out the right way - Many people make the mistake of locking out by flaring their ribs and hyperextending their lower back instead of using their glutes and hamstrings. This will not make your lower back very happy.
3) Before you descend, take a deep breath in and brace your core and squeeze your glutes. Reset after each rep.
4) When you are descending, you should extend your knees, but be sure that they do not hyperextend. Your muscles should remain engaged the entire time.
5) Make sure that your feet remain in contact with the platform the entire time. Some people opt to press through their heels when they are returning to the top, others choose to press through their toes. Do what works the best for you.
Now that you know what it takes to perform this exercise, it's time to build up your posterior chain.