1. Cast your net as widely as you want.
This is the fun part of the process. Look at anything and everything. No holds barred. If a school in Dallas appeals to you, put it on the list. If one in Lakeville, Connecticut floats your boat, add it to your list. You should end up with 15-20 schools on your first list. Be sure to visit each one virtually. Most schools will have videos so that you can get an idea of what the schools are like by watching the videos. This is not a substitute for visiting a school. It's merely the first pass.
2. Create a short list of schools.
This is where you have to determine which school or schools will be your safe school. What exactly is a safe school? It's a school to which you have an excellent chance of being admitted. It's a school which perhaps is not as competitive as some of the others on your list.
That is the challenge of the second step in this process. You must determine as accurately as possible which schools are genuine reaches or schools which you have a very small chance of getting in. Yes, anything is possible. But you don't need to be relying on a miracle to get you accepted at a school.
How do you figure out which schools are tough to get into and which are not? You do it two ways: you look at the data on this site. When you see acceptance rates of 25% or less, then that's a very selective school. As a rule it will receive 2 to 4 times the number of applicants for which it has places. It's very competitive to get into. You will have to have everything the school is looking for. Failed subjects and expulsions will probably get you off their list fast.
As you develop your short list, sort the schools into three tiers. Tier 1 can be the schools which are a reach. Tier 2 can be schools which you feel you stand a good shot at. Tier 3 will be the safe schools.
Unless you are a private school consultant, you will find it difficult to create the three groups or tiers of schools. That's why you need a consultant. A consultant knows her schools. She can tell you whether your child stands a good chance of getting into a particular school or not. She can suggest alternatives.
In truth that school which is so very competitive is a wonderful school. We all know that. But so are dozens of other schools out there. Think of them as hidden treasures. They don't have the cachet of one of those old New England schools, but is cachet what you are really looking for? Finding the school which is the best fit for all your requirements is the real point of this exercise. Find that school and your child will be happy. That's a good thing.