Sometimes I tap on the client but I always tap with them. I usually tap on them only if I sense that I need to and that is something I can't define, it is intuitive. I am lucky enough to be able to feel the energy shift in the other person so if I'm not feeling a shift I know that not quite enough is happening and I will sometimes take to tapping on them. I always, always ask if it is okay. Practitioners who are licensed as clinical social workers or psychologist may have professional injunctions that prevent them from tapping on a client. That is not so true of others in the healing arts such as nurses, chiropractors etc. which obvious takes a "hands on" approach. I believe a good practitioner will actually follow intuitively the clients need and wishes.
RecentlyI was tapping along with a client on back pain and I could only feel the energy shift and flow as far as the ankles, so I switched to tapping on the client. Still I only felt the energy flow only as far as the ankles and not all the way through the body. I mentioned this to the client and told her that we would shift to a less used tapping place on the ankles. It was then that she told me that she had injuries to both ankles including one bad break! Including tapping on the ankles worked and we had shifted the set-up to include the ankles.
A good EFT practition will trust their intuition and use it to guide them. If someone is uncomfortable being touched of course they should not be, but it would have me wondering why. I have had perfect strangers allow me to tap on them. If someone is guarded like that there is possibly an underlying core issue there to be addressed at some point in the process.