As a student pilot, there are many things taught in training, but I've found that one of the things missing from training is "real world" flying. For example, I don't really know what you are supposed to do when you land at an airport and you are not just taxiing back for departure. Say you need to top off your fuel tanks, what do you do? When tower says "say parking", what if you don't know where you want to park? How do you know where you can park your aircraft? Can you just pull up to an FBO and expect them to show you to a parking spot, or do you have to call ahead of time or on the Unicom? How do you tell them that you want fuel? If someone could just explain basic FBO operations and how to park and fuel up etc, that would help me out a lot. Thanks!
It depends on the FBO in question, but I'll outline the experience I've seen in the real world flying to various types of airports. Ill split it into two scenarios "big airports" and "small airports"
Big Airports: Generally at towered fields (think Class C, D and B that support GA operations) after landing (if you dont ask for a new clearance) they will say "say parking" at which point they will expect you to tell them where you are going. Like any other part of a flight this takes some pre-planning and FBO's are listed on places like airnav or in foreflight. This will allow you to pre-select an FBO based on services or fuel prices. If you land without knowing (say a diversion etc.) you can simply respond with "I need fuel" or "FBO" and they will tell you where to go.
At busy airports or airports where I suspect parking could be an issue I will typically call ahead and confirm there are spots or confirm they have the services their site says they do.
At bigger fields they often will have a marshaler to direct you on the apron you can tell them you need fuel once you shut down your aircraft. If there is no one to direct you its often fairly obvious where you should park (big open area in front of the building). Once parked if you are not greeted you can either try to hail them on UNICOM or walk inside and ask for fuel.
At bigger fields you are likely only able to get on and off the field through the FBO, they tend to be 24 hours and they will want their fees!
Small Airports: At the smaller un-towered fields (think 3000ft and under single strip out in the middle of nowhere) there will generally be only one maybe two options for parking/FBO's. There is often only one apron and it should be pretty obvious where the tie downs are. If you ask for fuel on the UNICOM after landing they will likely send the line kid in the fuel truck. Half the time they will send the line kid to point to parking but I would not expect it unless I ask over UNICOM. There is a good chance the airport is unattended and you may just need to park where you can and remember the UNICOM frequency since its likely the gate code. These fields often have self service fuel along with trucks since they may be unmanned.
I'll call small airport FBO's if I have questions about the local area, want to make sure courtesy cars are available or they actually have fuel in the storage tanks (yes sometimes they are out of fuel). However there are plenty of cases where I have just flown into a field, parked, and poked around the local area without calling or even speaking to anyone in advance.