Applying to a private school is a process. It is a process with many sections and parts to it. If you are accustomed to managing projects and meeting deadlines, this is just another version of that kind of exercise. I strongly recommend that you set up up just as carefully as you set up a major 12 to 18 month project at the office. When you organize yourself this way, you can put the project on the back burner for a week or so in the first six months without losing any momentum because you have your notes and 'Must Do's' listed. You can see what has to be done at a glance.
Start the process well in advance.
Begin your private school search at least 18 months in advance of when you actually want your child to begin classes. For example, if you want your child to begin Grade 10, then you would begin your private school search process in the spring of Grade 8. That will give you summer and fall to identify and visit schools. That will also allow time for admissions testing and submitting applications. You can start earlier if you prefer, but this timetable will give you enough time to thoroughly research and visit schools without feeling rushed. You will be able to arrive at well-informed decisions about where to apply. Starting far in advance ensures that you have enough time to take care of all the details and arrangements involved with visit schools