Come with bare nails if you can
If you are wearing a set from somewhere else, say so when you book so the slot includes a removal. Turning up with acrylic on and a ninety-minute booking means either a rushed removal or a rebooking, and neither is a good start.
If it is your own polish, do not bother taking it off. It comes off in ninety seconds here.
What the consult decides
What you do with your hands. This is the question that actually determines the answer. Typing all day, lifting at the gym, gardening, playing an instrument, small children: each of those rules something out, and it is much better to hear it now than to pay for a set that fails on Thursday.
Shape. Read choosing a shape if you want to arrive decided. Almond and squoval survive most lives; stiletto and long coffin survive almost none of them.
Structure versus length. Most people book length and need structure. If your nails bend or peel, builder gel will do more for you than an extension will.
Afterwards
Nothing to avoid, nothing to recover from. Cuticle oil once a day is the whole aftercare, and it does more for how long a set lasts than any product you can buy.