How do you write a thank you speech to my coaches?

I'm captain for softball and tomorrow is our banquet, I forgot all about writing a speech and I have no idea how to start this speech off. I'm 16 and I want to sound professional and serious. I had two coaches this year and they were really really good coaches so I want to thank them for all they've done this season. Please please please help me with ideas and how to start this baby! Merci =]