Collect what you need before the client arrives rather than at the chair: sensitivities and allergies, medication and conditions relevant to the service, what has been done to their hair or nails before, and what they are hoping for. A client filling this in at home gives you better answers than one filling it in with their coat still on.
Consent to the service is separate from a health questionnaire and should be recorded as such for anything with a real risk attached — chemical services, anything with needles, anything semi-permanent. What matters is that they were told what could go wrong and agreed anyway, and that you can show it.
Photographs need their own consent, and it needs to distinguish two different things: a photograph kept in the client's record so you can see what you did last time, and a photograph published on your page or your social media. Plenty of people are happy with the first and not the second, and assuming otherwise is the single most common way studios upset clients who were otherwise delighted.
Record consent where it lives with the client rather than in a notebook — on their record, with the date. Consent given three years ago for a different service is not consent for this one, and re-asking is a ten-second question.
A refusal is an answer, not an obstacle. Note it, honour it, and do not ask again every visit.