There are 2 basic principles with EFT and these are clearing "the writing on our walls" and removing "energy disruptions" from our energy system.
There are dozens of different ways within EFT to do these 2 things and I use many of them in my day to day practice. Some of the advanced ways are very powerful indeed.
One of these, The Personal Peace Procedure, clears all the charged emotions and energy disruptions attached to all the events of our lives. People report having a profound sense of peace when they complete this procedure. I use muscle testing to indicate when it is complete. I find that people who try to do it wiithout muscle testing, can end up with hundreds of issues remaining that they missed. Most people have many hundreds of issues to clear, and so it takes quite a few sessions, but those who have done it report an improvement in their health and in their lives, and they speculate that future health issues that they may have otherwise had, will not now occur.