The patient must consent to each element of the procedure, including all known implications. Otherwise, the contact will constitute battery - otherwise known as contact without consent. For example, a doctor will still be liable when the patient consents to an operation on the right ear and the doctor instead decides to operate on the left ear. While the doctor may have poorly assessed need in choosing to operate on the right ear, s/he needs additional consent to operate on the left ear.
Further, the patient should consent in written form, so it can be proved in court. Moreover, the information on which client bases his or her consent should be written, so it can be proven in court as well. Here, the writing should be sufficiently clear to inform the average patient. To help, bold or italicize relevant provisions.
Only engage in procedure that is accepted in the field.
A doctor will breach the duty owed to his/her patient if s/he practices in an "unreasonable way" as compared to other doctors.
What is an unreasonable practice? Well, that is based on what procedures other doctors engage in. Thus, a doctor will only act negligently when his procedure is one that other doctors would be unwilling to institute. In some states, it can be more based on "accepted practices" - but this is less common than it used to be.
To be safe, engage in procedure that other doctors engage in. That will absolve you from breaching your duty of care.
Do not practice outside your area of expertise.
You might be more likely to use unaccepted procedures when you are non-expert in a field. Do not practice in a field outside your comfort zone. For example, lawyers are guilty of negligence when they are not sufficiently educated in a field to help a client in a case in said field. A similar standard should be observed for members of other service professions. Otherwise, a judge might be unforgiving of otherwise innocent error.
Make a written record of what you did and didn't do.
When multiple doctors help a patient, it can be unclear who negligently caused harm. Hence, all might be deemed liable when only some were actually at fault. By keeping a record, you can prove that you did not cause the harm.
Maintain a thorough record of every injury your patient suffered from at the time of arrival.
Patient might claim that you caused harm which was already present. Do not make yourself liable for any harm you did not cause. In order to prevent liability here, thoroughly investigate for present injuries.