A visit to a facialist should not be any different than a visit to a medical professional (or a hair dresser for that matter). You need to trust the person who is going to take care of your skin. Hair grows back after a bad haircut (that was how we kept consoling ourselves after a couple of frankly disastrous run-ins with bad hairdressers). Your face is... well... your face, whoever gets to lay hands on your face needs to know what they are doing.
Ask for recommendations
If you have never visited a facialist before, ask for recommendations. Chances are a friend, a colleague or a family member knows someone and can give you a recommendation. If they can't, look for recommendations online. It goes without saying - if you decide to go for a specialist treatment (things that come to mind would include any type of laser, milia removal, microneedling for example), do look for facialists who actually trained to provide the treatment.
Once you decide on the place, call beforehand. If you have a skincare routine and use actives (retinol, acids, vitamin C), do ask if you need to remove them from your routine a couple of days prior to the visit.
Do some research beforehand
Many salons and spas offer a wide variety of treatments. It can be anything from a classic facial to microneedling, lasers, and peels. Even though a good facialist will guide you through the process, it is prudent to do some research just to get a general idea what you might expect. Things to consider would include what type of machines are used, how many sessions you might need to get optimum results, should you expect any downtime, is there anything specific you should be doing to take care of your skin post-treatment, etc.
Two days before a big event is not the time for extractions or treatments that require someone downtime. Treatments that aim to soothe, hydrate, plump up the skin are ok.
During the visit
Any good facialist will do a consultation before they treat you. They should learn about your skin, what kind of sensitivities or allergies you might have, get information about any possible medical conditions and medication you might be taking and what you would like to achieve with the treatment. Likewise, they will ask you about your routine and the products you use.
As mentioned previously, they should guide you through the process and explain what they will be doing. If you have any concerns, please don't be shy about asking questions. Now is the time to speak up.
Last, but not least - wear comfortable clothing. It does depend on the treatment, but chances are you'll be there for a while; you need to be able to relax (that's the whole point).
Do you go for a regular facial? How did you find your facialist?