What matters?
That the welcome is warm, and receptionist ready and aware of the scheduled appointments
No matter whether the therapist or receptionist, everyone is aware of small things such as what's the tea served that day (assuming the flavours change from day to day)
That if guest ticks off a health condition in the questionnaire, this must be acknowledged and care is to be shown. If guest states he/she has migraine or high blood pressure, ask about them and inform what you would do differently during the treatment. Don't simply ignore the information.
Still on the health form: crossing X to highlight areas to avoid and circling to indicate those to focus on in the outline of a human body form is the easiest. Don't make us write out and then add another level of inefficiency by asking us what we had written. (Idea: in a standalone spa in Hanoi, they have a smart hand-gesture system which they inform the customers prior to the treatment. Raising one finger means softer/gentler, two is to make it a little stronger, and three indicates much harder. This helps to eradicate any language barriers in the treatment room.)
Don't be rigid - if the guest mentions first that the air conditioning and lighting are fine (because we know what you want to ask so we may simply get onto it first), please do not ask these very same questions just two seconds after.
When guest is asked how's the room temperature, and yet the air conditioning is centrally controlled and can't be adjusted. If that's the case, modify the question to make it a simple: "Are you comfortable?" or, "If you feel cold, I can cover you with additional towels/blanket."
When holding up the towel to disrobe, understand that this is about giving guests privacy. Hence, do not peer/peek over the raised towel, even if the guest is speaking to you. Hold it high enough, and please, do not turn towards the wall mirror because if you can see us, we can see you looking too.
Please pad the counter top or other surfaces where the bottles are placed. Klanking noises do not help guests to relax.
Don't wait too long once treatment has started, to ascertain satisfaction about the pressure. Some guests fall asleep almost right away and it may interrupt their peace. (Even though the initial 5 - 8 minutes is more about stretching and warming up, guests can usually already gauge if the therapist's pressure is fine or otherwise. Recommendation: ask within the first 5 minutes and no talking after that, unless guest engages with the staff.)
When asking guest to turn over at mid-way through the treatment, please don't chat or ask questions. (Once again, unless initiated by the guest himself/herself.)
When guest says "no oil in the hair", please do not touch, fondle, smoothen the hair with oily palms.
Do not squeeze out the blackheads or whatever on the guest's back during the massage. If at all, ask at the end of the treatment in order not to disrupt the rhythm and sense of relaxation.
Do not upsell immediately after treatment is completed and when guest is still in a half drowsy mood. It is just not the right time. Instead, give some advice for their benefit - e.g. drink more water, detox with hot water and lemon in the morning, do more stretches or shoulder exercises, apply hand cream especially to the elbows (or other specific areas), etc.
When signing off the bill, offer a specific assistance even if it doesn't pertain to the spa's department. E.g. for the last treatment of the day, offer a wake-up call tomorrow or a hot drink to be sent to the room before sleep.
A genuine, warm farewell.