The only time I call an FBO ahead of time is if the airport diagram is confusing or I need a rental car. That happens about 5% of the time. Otherwise, I just fly in and figure it out from there. If there's a tower, they'll give you taxi instructions to general aviation parking unless there's more than one option and then they'll ask, so just be ready with an answer. If there's no tower, find your own way to where you want to go and avoid any big red lines for commercial airline security areas.
Be aware that sometimes where you turn from the taxiway to the ramp will make a difference between a marshaller from FBO #1 running out, one from FBO #2 running out, or nobody running out because they think you're going to tie your plane down yourself. Sometimes the marshaller is also doing something inside and can't run out, so be prepared either to see a marshaller or to find your own way. If you aren't sure what to do, it's best to call before your flight and ask. I think it's fair to tell them, "Hi, I'm a pilot and I'll be flying into your FBO tomorrow morning. Which taxiway turnoff should I use so I don't get directed to your competitor?" But if you get there and you're not sure what to do, it's also fair to pull into a tiedown spot or to pull up to the FBO and shut down to ask.
Mostly, if you don't hit any other airplanes or people, you will be fine and you'll learn as you go.
Two pieces of advice I do have beyond "don't worry and just do it":
1. Bring your own tiedown ropes or ratchet straps, whatever you prefer. And learn the proper way to tie down a plane using chains. Many airports provide ropes or chains but many others do not. Having a set of ropes with you and not having to ask for help with tiedowns will save you a lot of trouble in your journeys.
2. You are a pilot first and foremost until you are at least off of the runway, and to be safe you are a pilot until the engine is stopped. Once you are safely on the ground and deconflicted from other traffic and people, you can become an avgas customer, tourist, or whatever else you flew there to be. Don't get distracted calling an FBO on UNICOM or looking for where the fuel pumps are when you should be talking to tower, looking for traffic, or running a checklist. Distracting yourself from flying the airplane is how you do things like forget to push the mixture forward or to put the gear down.