Keep your focus, as much as possible, on the person you are communicating with rather than the interpreter.
For clarity, address each other directly in first person: Desirable: “What do you think?” Less Desirable: “Ask him what he thinks?.”
When possible, share any notes, outlines, or handouts with the interpreter in advance.
The interpreter would appreciate getting the names of people and places in advance as well as any acronyms or specialized vocabulary that may be used.
If, during the assignment, you plan to turn down the lights, remember to leave enough lighting on the interpreter.
The interpreter may request/suggest specific seating/positioning to facilitate the best viewing angles.
Speak in your normal tone and at your normal pace. The interpreter will tell you if you need to pause or slow down. Putting white space (pauses) between complete thoughts/sentences is preferable to slowing down your overall pace. This is because the interpreter may not be able to proceed with the interpretation until it is clear what your complete thought is.
People often read aloud faster than they naturally speak. When reading extensively from written materials, consider supplying a copy to the interpreter and be more aware of your pace.
Remember that the interpreter is responsible to relay everything that they see/hear. Don’t assume because you are not addressing the person directly that the interpreter will not convey anything and everything they see/hear. Asking the interpreter to not convey something you’ve said or are about to say puts them in a very awkward position.
Don’t worry too much. Bruising fades after a few weeks and scarring is rare. : – )