This answer is based upon: my own experiences of receiving 6 sessions of chiropractic treatments in my mid-20s; what former chiropractic patients tell me; and my own knowledge of the history of osteopathy and chiropractic. Despite the differences in approach, it is impossible to overstate the importance of finding someone with sincerity, integrity and empathy. Most practitioners are driven by a desire to help – if you sense that this is secondary to making money, be wary.
Time – typically osteopathy sessions last 30 minutes, while a chiropractic session lasts 15 minutes.
Duration of treatment – be questioning if you are asked to commit to (and pay for!) a specific number of sessions. It is often difficult to predict how many sessions will be needed, although your practitioner should be able to give you an estimate based on the nature of your condition/problem, your age and general fitness. Some people choose to have regular maintenance treatments in order to help them with a demanding/stressful job, or to manage a chronic condition, such as spondylitis (osteoarthritis of the spine), or large joint osteoarthritis. Be questioning of special offers (“Get 10 sessions but pay for 9”) and discount vouchers.
Philosophy and practice – when Dr Andrew Taylor Still (a medical doctor) was teaching osteopathy in the mid-late 1800s, one of his students was Daniel Palmer, who later founded chiropractic. For unknown reasons Palmer decided to pursue his own version of osteopathy, and went on to call it chiropractic. “Chiropractic posits that subluxation of the spinal column and other articulations can affect nervous system function and the expression of health, which may result in symptoms, infirmity and disease” (http://www.palmer.edu/Our-Identity/#Philosophy_Statement). In practice, most chiropractic treatments consist mostly, sometimes exclusively, of clicking joints (“adjustments”). Osteopathy is essentially a treatment informed by a philosophy which is based upon viewing the body as a holistic unit, and working with the body to find healing. It is difficult to define osteopathy as a series of techniques or manoeuvres, although to make it easy to understand, patients can expect their osteopath to use techniques to massage/stretch the tissues, mobilise/articulate joints, possibly click joints if appropriate. Some osteopaths also use what is known as cranial osteopathy, which (despite its name) is an extension of osteopathy and is used to treat the whole person and not just the head!
X-rays – most chiropractors have X-ray facilities. In my experience a thorough examination and careful questioning reveal the condition of an underlying joint. An X-ray should only be used if there is some uncertainty over the diagnosis. My advice is to think carefully about subjecting yourself to radiation, and to always ask “what will an X-ray tell you that you don’t already know?”