Good mornings are the staple of a WSB max effort day. This is for several reasons:
1) Because they work your posterior chain in such a manner as to benfit both the squat and deadlift.
2) Are less demanding on your body than either squats or deadlifts and are easier to recuperate from.
This being said, it is imperative that one does these with proper form.
I was lucky enough to have a powerliftering coach at my old gym to show me proper form on these.
If you have access to one, this is the way to go. Even if you have to spend 40 or 50 an hour, it will be money well spent. This is your back that we are talking about here. Honestly, I would have someone teach you all of the big three and be diligent in trying to master your form in any lift.
If not, try to get a decent training video somewhere.
However, they are not rocket science and are less technical than either a deadlift or a squat.
Simply step up to the bar as if you are going to squat. I recommend starting off by doing wide stance arched back good mornings.
Set up with a wide stance which for me is with the front of my feet an inch from the bars of a power rack. I point my feet outwards, while arching my back while keeping my head straight.
Then push your ass back, straight back until you lower the bar; go down until you feel like you are going to lose the arch. All the meanwhile, do NOT look down and keep your eyes ahead; if you look down, you will start to round your back.
When you are ready to ascend, pretend that a blond with big tits and an ass that tastes like french vanilla ice cream is in front of you, and move your hips like you are trying to tap that ass.
Repeat the process for a 5 rep max.
Have a spotter watch you.
When you get your form down, try for a 3 rep max.
Things to watch for:
1) Losing the arch and rounding the back. While you can do round back GM's, I think that they are riskier than arch back ones.
2) Tilting to one side: this means that you have a weakness. Lower the weight.
You can also vary your stances. I usually do a wide stance because I pull sumo. If you pull conventional, you might want to keep your legs closer together.