I am planning to get facial fillers; please let me know the precautions before and after the procedure.

My face has suddenly lost so much volume that even makeup can't cover it up. I've finally decided to take the plunge and get fillers injected directly into my face, so I've already booked an appointment. Now that the date is approaching, I'm suddenly getting scared and anxious that something might go wrong. Since this is my very first time getting a dermatological procedure, are there any specific precautions I should follow before or after getting the fillers? Like things such as not sleeping on my stomach or avoiding saunas. I feel like I'll only feel at ease if I know everything thoroughly beforehand. Please share some tips, those of you who have experienced fillers!