Welcome to the forum mate.
Just relax as much as you can and enjoy yourself. Don't focus on what can go wrong as you are only putting yourself into a negative mind set before you even start! Creating a little self fulfilling prophecy for yourself...
Focus on what you can control - know the laws of the game as well as you can, make sure your kit is correct and that you take out everything you need (watches, writing implement, cards, WHISTLE, flags and a coin), nice warm up and a big smile.
And no matter how it goes, even if you are in fact the fabled "worst ref in the whole flipping world" that we occasionally get called (and we all pretty much do suck to various degrees in our formative games) don't worry about it. This is a learning process and you will get a damn sight better with time, reflection and hard earned on field experience! (of course if you start out already awesome, then lucky old you - premiership here you come!
)
And don't forget to make use of the experience of other refs; your local RA being a good source of support and advice and of course a certain referee forum you have already stumbled upon....
Good luck fella and let us know how you get on.
