Groundwork in Earnest
Groundwork is teaching your horse while you are on the ground, not mounted. It should begin while the horse is a foal. Groundwork may involve teaching the horse to lead and stand still while being groomed, teaching her to tie, exercising the horse on a lunge line, and driving her with long lines. If you do the groundwork well, the good manners the horse has learned should transfer to her training under saddle.
There are some key things you need to teach your horse to help ensure your own safety on the ground. One is respect for your personal space. Another is stepping over the hindquarters, perhaps the single most useful move your horse needs to know.
The goal is to have your horse learn that if you turn his head to the right and liven up some energy with your hand, arm, or the end of the lead rope (or eventually your mind), he is to step his right hind foot underneath him in front of the left hind foot, and step his whole hindquarters to the left — and vice versa for the left. This move not only expands your horse's bend and flexibility but also makes it possible, for example, to step your horse out of a corral full of other horses clamoring to get out, or to step him into his stall and turn him to face you while you remove his halter and step out to latch the stall door. The list of situations for which this step comes in handy is endless. As with all other groundwork you do, this move is pretty useful when you are riding as well.
Your horse also needs to understand that she is to yield to pressure, not brace against it or fight it. When your horse thoroughly understands this, you should be able to simply place your hand on her side with meaning to get her to step away from it. If she accidentally steps on the lead rope and pulls on her head, she will back up away from the pressure and free the lead rope rather than fight against it and rip it out from under her foot. The only time it is safe to tie your horse is after he gains a thorough understanding of yielding to pressure.
Understanding how to yield to pressure may also be helpful if your horse gets caught in, say, fence wire. There is a much better chance that he may not panic and struggle; instead, he may wait to be released and will not hurt himself too badly.
Yielding to pressure also means that when you put your horse's halter on, she drops her head and helps you get it in the right place. She doesn't throw her head up as high as she can, making it more difficult for you to reach. If you need to back her up one step, you can ask for one step. When you get it and release the pressure, one step is all she'll move. True yielding is not a conditioned response method; it is truly meaningful to the horse.