Very simple, there are 141 girls and hotel girls
141 girls you don't need to call, just find their address, turn up at the door and see if the door has s welcome sign, if it says please wait, the girl is busy so dont knock/ring. If it says welcome just ring/knock, she will take a minute or two to get ready but she will open the door. You decide if you want her, if not just say sorry, wrong door and walk away.
If you do want her, step inside, tell her if you want the full package or just part service and confirm the price just to be sure. The standard routine is you get undressed, take a shower and give your little bro a good clean wash, some girls will wash you, some you wash by yourself. Then its either a massage or straight into the action, the type of action that each girl does varies, if you are bold or have seen the girl before you could try some requests, some girls will do extra requests for free, some will charge extra and some won't do anything extra. Don't ask me what you can request, use your imagination
The buildings these ladies work in vary from old to very old and they may look dirty and dangerous, they are safe, at least the several ones I have been to. Some even have a porter/door man, don't worry about it, just be confident and walk right in, they will not stop you. Some buildings have a key pad lock, if the girls page says password 1234, then 1234 is the number to get into the building so make a note of it.
Hotel Girls you must call a number, her agent will pick up and you tell him/her who you want to see, they will tell you to either wait xx minutes or they will you back or the girl is not available and they will offer you another. Once you confirm you want to go ahead, they will tell you where to meet, you go to the meeting place, usually in busy street or outside a hotel.
At this point you are perfectly entitled to leave if you don't like what you see, also beware a lot of agents will present a different girl to the ones in the profile photos. If you like what you see, the girl will acompany you to her room in a hotel, again the usual routine is a shower then various services and you pay once you are done.
Yes, always use protection, for the safety of yourself and the girl, some girls will agree BJ without but personally I wouldn't risk it. Read the reports for suggestions. The rates are listed in the profile descriptions, outcalls can be negotiated but not all girls do outcalls, most make enough just working the day shift and are too tired to work outcalls.