The format is the first thing to settle. Some escorts host only at their own address and others travel to the client's accommodation; a few do both depending on the day. Asking in the first message saves running around, because it changes the logistics completely: if you're the one going, you need the building reference; if she comes, the place has to allow visitors.
Contact is made from the ad itself, almost always on WhatsApp. Write at a reasonable hour, with a clear, direct message, and confirm on the day itself a few hours ahead. Schedules here fill up in advance rather than on impulse, so leaving the booking to the last minute usually ends with no slot left in that day's diary.
As for what you can look for, the range runs from a short meeting to a long date with a night out first. With restaurants a few blocks away, being accompanied to dinner is a common request, as much as massage or the close, unhurried treatment some profiles describe as GFE. Anything not stated in writing is best not taken for granted.
Discretion here comes almost by itself, but it's worth not breaking it. In buildings with controlled access you announce yourself over the intercom and whoever is waiting already knows what time you're coming, so there's no need to explain anything to anyone. Turn your phone volume down, avoid conversations in the lobby and go straight up: the neighborhood is quiet and any noise carries.