Miranda,
Thanks for the kind responses everyone! Great advice! Miranda I had to go back to check your age...You are only 16! My neice is 15 and is going through the same thing. She is so vivacious at home however, which is when she comes 'alive' . This explains the fact that perhaps, you should try explaining and expressing yourself with the people your are most comfortable with(i.e. family). You could see this like a rehearsal of sorts. If you have a best friend or sister , brother even Mum would be willing I am sure to 'role play'.
So yes it will be different when its actually someone else, but at least you will find you stumble less etc., so have a list of questions you are more concerned with if/when you go on a date(people do this for interviews and presentations too). Have them ask you some 'popular dating questions' or (you know best the scenarios in which you feel clumsy) and answer, do this say once per week or whenever there is some extra time..Actually carve out some time just to this if even one question daily or weekly. This along with the great advice above you will be on your way.
There is also Toastmasters(check them out online) I should start a Toastmasters for Teens eh? (:-
I was never this concerned about being shy at your age..and then I got to Grad school and had to give Grand rounds weekly huge auditorium with medical professionals and researchers..Yikes! I got over it, but it is great that you are only 16 and are starting NOW rather than LATER ..by the time you get to be 20 (and I am sure you will before then) (:- Everyone will be telling you (hopefully tactfully and nicely), to speak less...
Don't worry..You will be fine. There are worst things to be and to worry about and overcome at your age-We have your back Miranda..You will overcome this one-not impossible. Good luck and let us know how you are doing! Take care.
"Remember to always celebrate the beauty in you"