This last weekend was the solo/ensemble festival at Chico State, and I did a horn solo. I played Mozart's Rondo(my brother gave me the Mason Jones horn solos book for Christmas), and I didn't do very well. I still got an Excellent rating, but when my mouth got dry, some of the fast/low notes just didn't speak. That was my second solo, the first being nearly a year ago(before braces), and that was just at a small Youth Symphony concert, plus, that song was fairly easy for me to play with the amount of practice I'd put into it(Strauss' Nocturno). Oh, and for honor band, our audition piece was Beethoven's Sonata for horn. For both the honor band audition and this last weekend, I can play the songs perfectly beforehand, but about a half hour before the performance, when I'm warming up, I start to get nervous, and I end up doing terribly. I never get nervous at all for ensemble or other group performances, but by myself, I get really nervous. I'm hoping I can get over it within this next year(just in time for the next solo/ensemble festival), but I don't know if that hope will come to any fruition. Practice, practice, practice, I guess. Just in case, I'm starting working on that solo for next year; I really want to do Villanelle, but I'm going to save that one for my senior year, so I was thinking go with one that's a little easier, like I See a Huntsman. Part of the problem with doing Rondo was that it is a pretty difficult piece, and nerves didn't help.
It can get easier, and then some people just never get over the nerves. Lot's of people will offer up suggestions to overcome some of your nerve issues, like chew on your tongue softly to get the saliva glands working. And that works if you have the time to wait - usually Mozart goes by so quickly there isn't enough time.
I would suggest practicing in the condition you get nervous. So, if your mouth gets dry when you play by yourself you can do this - - - get some saltine crackers and put them in your mouth (don't chew them but munch them enough to get them to absorb all the wetness in your mouth. take them out and practice your solo. Do this a few times and then when you do get dry mouth you will be able to play with the dry mouth.I encourage my students to play without licking or moistening their lips. It accomplishes three things. 1)they get fewer cases of chapped lips. 2)They can play when their mouth go dry. 3) I think it produces a better tone when done correctly.
I've found nerves start to get better after you've been through several experiences like that. When your nerves start to get bad, simply relax, literally sit down and try to relax every muscle in your body. I wouldn't recommend completely taking your mind off of things about to happen, but try to get it in your head that the standards aren't as high as you may think (and most likely, this is true if you're starting to get nervous).
I used to freak out about any type of audition. This last audition I did, I felt myself feeling nervous; so, when I went into the practice area, I made myself play veryvery long tones and such to try to slow things down. It worked. -thats just my 2 cents
I have certain rituals I have to follow before a performance, otherwise I completely freak out... It's a little crazy but it helps me to relax a bit and concentrate. Just have self belief, imagine it's just another rehearsal. And always think to yourself, what's the worst thing that could happen? A note doesn't speak or is slightly out of tune. Unless you're playing to a very discerning audience then it's unlikely anyone will notice. The number of times where I have been nearly in tears after a performance - "it was terrible, I completely messed up, never playing in public again bla bla bla" and people in the audience thought it was good and didn't notice any mistakes...it's quite funny! I'm not saying let yourself become complacent, just remember that it's not the end of the world. And if it IS an important one, e.g. an audition, then there should be an experienced horn player there (on the panel or whatever) who knows what it's like, and knows how horn playing is so easily affected by nerves. They should be able to see past the nerves and see what potential, talent, technique etc you have. Good luck!
Another thing: nerves are a lot better when you know the person/people who are listening. For example, when I auditioned for band I felt fine (I know my band director very well), but when I auditioned for the local orchestra last fall, I was even shaking it was so bad (I didn't know the director at all then). So if you have a chance to meet the audience before hand it might help.