The main thing with the Probe is that you need to eat normally, since it is measuring the intraesophageal bolus transport and well as incidence of acidic Ph. As you swallow, the peristalsis of the esophagus will tug on the probe which can be annoying. From my experience, staying away from foods that are sticky or dry (hard to swallow) will make the entire "experience" easier for you. Drinking water is important before and after bites as it "lubricates" the probe (and esophagus) making the bolus easier to swallow. Taking smaller bites does help.
Be sure to live normally during the 24hr period, even if it brings on reflux - that's the whole idea.
You will have a digital data recorder with buttons to indicate normal position (i.e. Sitting up or Standing) and Supine (which is laying flat.) It's really not that hard and I'm sure that the doctor or technician will explain everything to you. I suggest having your own questions written down on paper, so you don't forget.
One last thing. Do not pull on the probe or attempt to adjust it. It will probably be taped to your nose and neck.
Keep the data recorder slung from your shoulder and close to you when sleeping, so as not to induce movement of the probe by turning and tossing. Also, don't let the recorder fall down, as it might pull your probe out, under weird conditions.
Hope it goes well!
P.S. Bill, If you remember the name of the device that measures Akaline (bile) please post it here. Thanks.