The first thing is to establish yourself as the leader of the herd. Don't let this mare misbehave in any way, not even a smidge because is you give an inch they'll try to take a mile. This is just what I do, by all means do what you are comfortable with, with these posts and research put together a regimen and go for it.
1. Again establish yourself as the herd leader. Halter the horse and lead the horse where you want to go. If you are going through gates or into or out of a barn you go through the doors first. Halter and tie the horse before you feed it every time. You are showing the horse that you are in control of the feed, but that you are also a good provider.
2. The first year (halter training, leading, tieing, holding feet, tacking up, all ground work) keep the training sessions short, 30 minutes or so, but positive. If you get hitched on something you are trying to train and the mare just isn't getting it, ask her to do something she knows, praise her, then take a step back. Ask yourself why she isn't getting it. Is it you or are you asking her in a way that needs to be changed so she does get it? Use longeing to teach verbal cues such as walk, trot, the canter, and whoah. Anytime when saying whoah, riding or leading, it's not a request it's an order.
3. When first saddling go slow. The first few sessions get the horse used to having someone "up there". Ponying the mare alongside another horse is a great way to help her overcome her fear of having someone above them. Remember a horse is a prey animal and has instincts that say anything on it's back is bad. They are showing a lot of trust in us to allow us to be up there and lead them where we want to go.
4. As the mare accepts to be ridden increase your time in the saddle. Wet backs and blankets will make a good horse. The first thing I teach a horse is to whoah. When things go sour you want to have the confidence that she's going to stop. Then walk, trot, and finally canter. The first summer I ride a horse, that fall they are turned out until the next spring. Remember, at one time or other every horse is going to come up with the idea that they don't like all of this new work and will rebel in one degree or other. You'll just have to work through it.
5. Make a plan. I sit down and lay out what I want to teach this horse this year. It's different for each horse that I train because some will learn faster than others and some are trained for ranch work vs. pleasure competition. However, when working with animals this plan isn't set in stone. You can lead a horse to water, but you can't make them drink. Also don't move onto something new until you have accomplished what you have set out to do. Example, you want to teach a horse to stand quietly for a farrier but they are acting up, don't move onto something else. Stick it out and you'll end up with a better horse in the end.
This is just what has worked for me and my wife, but feel free to completely ignore this whole post if you desire, no big deal. Good luck!
"The cow is nothing but trouble tied up in a leather bag." - John Wayne in "The Cowboys"