I've been fortunate enough to do many concertos with student soloists, always an interesting experience. Here is the sum total of my wisdom in DO and DON'T form.
DO try and know your speeds beforehand. Most inexperienced soloists have spent much more time playing on their own or with a pianist than with an orchestra, and don’t realise that, even with the Classical repertoire, there is a great deal of subconscious tempo variation. In other words, you will play some passages quicker or slower than others without being aware of it. It helps enormously if you can tell the conductor which ones these are beforehand. This doesn’t just save time in rehearsal, it also gives the conductor time to work out how, for example, to get back into the main tempo when your more relaxed second subject has finished. It’s worth practising with a metronome, not because you are expected to play metronomically but because it enables you to judge where you want to push the speed on and where you want to relax.
DON’T watch the conductor too much. He will generally be beating slightly ahead of the orchestra, so if you try and keep up with him the music will get faster. As a rule the orchestra and conductor’s job is to keep up with you, not vice versa. It is sometimes the case that your passage-work is so fast that you have to follow the orchestra instead: one example is in the Mendelssohn Violin Concerto first movement just after the cadenza, where the soloist plays arpeggio semi-quavers over the recapitulated first subject: listen and play with them. There are many other examples in the standard repertoire.
DON’T be afraid to ask for things to be done differently. The orchestra is there to serve you. There are ways of doing this however. Don’t say to the orchestra directly, “Can you do it this way instead?” The conductor has probably spent some time with the orchestra, in good faith, getting the orchestra to do it the way you don’t like. Ask the conductor. “Would it be possible for the woodwind to ....." Nine times out of ten the conductor will be pleased to oblige. There may also be good reasons why the conductor has done it his way, reasons you aren’t aware of, and you don’t want to end up in a situation where the conductor is saying to the orchestra, “No, don’t do that. Do it the way I originally asked you”.
DON’T be nervous. You are probably the best player in the room, and the orchestra will think you are wonderful.
DON’T be arrogant either. The orchestra might not be as good at their instruments as you are at yours (although sometimes some of them will be), but the likelihood is that they will be vastly more experienced musicians who have seen young prodigies come and go. Send the conductor a card afterwards. Do you want another gig or don’t you?
DON’T play without the music unless you are 100% sure you can do it. You don’t want to ruin your opportunity for want of a music stand.
DON’T do things differently in the concert from the way you did them in rehearsal. As Beecham said, an orchestra is not a piece of elastic. It cannot instantly accommodate your interpretative whims.
