So, this doesn't apply to me right now, but I have been thinking about it. I have a friend at work, we'll call him my best friend, at least in my factory. Sometimes he worries about me, if I don't seem exactly right, which is great. However, he doesn't know I'm transgender yet (my transition won't be for another 2 years). He is also my boss's son, so I can't exactly tell him just in case.

My question applies to when I do tell him. I'm not sure what his reaction will be. Obviously you have good, don't care, hesitant, but you also have hostile (I doubt it, but I don't know). So, when you tell people whose reactions you're unsure of, is it better to do it in private, or in a public place. I could see both going bad if the reaction is hostile.

Maybe before coming out to him in public or private, fish for his thoughts on what he thinks of trans people. Bring trans issues like the bathroom debate, discrimination and so on up nonchalantly and guage his reactions.

lol. That's not so easy. We work in an all male factory (at least, the people on the floor are all male). Trans issues don't exactly come up where I work. I can't even begin to think of a way to bring up trans issues to him.

If you're not transitioning for two years don't tell him for two and half years. In fact, get a new job by then and never tell him. I wouldn't tell anybody until you are sure or are about to transition. Two years is a long time.

this is me trying to tell my guy bestfriend.. "dude check out this article (it's about ->-bleeped-<-) what do you think about it?" he said "why are you showing me this?" i said "what if im one of them?" he said:"i dont know man maybe i'll f*** you (his exact word)" i said"seriously man, this been happening for a long time but now i can't hide it anymore, i'm okay if you cant accept me but this is me and im not trying to hide anymore"

and we're still bestfriend, nothing change. if something we're getting even closer

Chelsea Ann your very name reminds me of an opportunity for you to just be discussing current events with your friend.  Big national (USA) news stories about Chelsea Manning's transition could give you the opportunity to ask what he thinks about her transition?  That he cares enough about you to "worry" when you're not right seems hopeful to me.
Peoples reactions really do vary and after coming out to people over and over again I assure you most will be more supportive and less hostile than we fear.  Still a rare person can be angry about not knowing or that we "lied" or whatever so being in a public place is a good idea.  You have a long time table but be prepared for the story to spread.  I told my best friends and closest family but even well meaning folks have a tough time not retelling this "news."  Practice and writing about it helped me.
We all own our identities and feelings and they come from between our ears.