Actually, I tried to use a repeater in Deland, Florida. It was my very first try and as soon as I made a reception test I got a reply from a person who very nicely told me that he could hear me. I made the mistake of using my GMRS callsign at the beginning of my transmission. I then heard the same voice asking my very nicely "who do we have here" and I repeated my callsign. I did not transmit anymore (I did not want to clog the airwaves with my newbie ignorance!) and I did not hear anything. Only later did I realize that I had not received any authorization to use that repeater. I don't recall where/how I found the frequency and access codes but I think it was on GMRS.com.
So my question is: would it be rude for me to access a repeater and ask for the right to use it even though to make this request I need to use the repeater once without any authorization?
I am a total newbie, but I really do not want to be rude or break any rule. I get it, repeaters are private and I have no "right" to use them. But if I don't get any replies to my requests, shall I try another way to ask or shall I assume that if the frequency and the codes are available I can at least ask for the use over the air?
I think that the steps suggested by MichaelLax make sense except that I would not interrupt a conversation already taking place. But if there is silence, why not ask?
Again, my apologies for being such a clueless noob!
PS: being in super-flat Florida, repeaters probably only make most sense in cities (the biggest "mountains" in FL are landfills!). Since I live in a small town and rarely go to big cities (I am more of a wilderness hiker) in most cases there are no repeaters I could use anyway (like in the Ocala National Forest or the Juniper Wilderness), so not using repeaters is okay by me. I just want to learn the proper way to do things.