Making a sound The best way to practise getting a sound out the instrument is to practise buzzing on your mouthpiece.once you manage to buzz a sound on te mouthpiece well it will help you be able to get a good sound.
High notes For this I would say practise playing notes rangeing from a bottom c to a middle G. This was a piece of advice that i got from Cameron Mabon and it has helped me a fair bit on my hiigh notes.
Reading music Reading music is a difficlt thing especilly when first starting, all I would say here is be patient and keep practiseing reading the notes and gettin the right amount of counts on each note and eventually it will become much easier.
Nerves The only way I would say to stop nerves is to just remember playing music is enjoyable. when I go on stage I now just go on to enjoy myself. and just tell myself that i am in my room practiseing, and that manages to relax me enough to play my parts.