Performing with an orchestra (first time)

[obtuserecluse]

Hello, pianostreeters! Recently, I friend of mine that's working on his bachelor licentatie conducting exam asked me to play Beethoven's Choral Fantasy Op.80. I haven't played with an orchestra before, so I'd like to know what are your advices for a situation like this, for performing with an orchestra in general and, why not, performing this piece specifically.