So you've got yourself organised to get to rehearsals regularly, and on time. What now?
Listen to recordings of the pieces you're rehearsing to help you get to know them. This really helps them stick in your head, and can often answer questions that you have about how something should sound. It helps rehearsals run more smoothly if everyone knows what the outcome is meant to be.
Listen to other people - both musically and in what they're telling/ asking/ suggesting/ discussing that you do. Listen for instructions about what you're doing next, which bar you need to play from, and how you need to try to play it. Listen when other people are being given advice or directions, because these could apply to you too, and they might affect how you play your part. If the conductor asks one section to play from bar 126, there's a good chance they'll subsequently ask everyone to play from the same place, so listen to that bar number even if you aren't playing this time through. Listen to how your part fits in - is it supposed to blend in or stick out? Listen to how other people are playing - do you need to match them or sound different?
Listen to people talking about their experiences and learn from them.
As mentioned in the previous post, I think a diary is vital - either online or paper, or both. Put things in it, soon after you know about them. Check it. If you forget to put things in your diary, how about setting an alarm to remind you once a week (or however often is useful) to sit down and update it?Same thing for checking it regularly. Stop trying to remember when everything is happening, and get it all out of your brain onto paper (or virtual paper).
Write notes in rehearsals, whether it's on the music itself (in pencil, or the librarian will scowl at you), or on a post-it note or in the back of your diary if it's not relating to a particular bar/ note but something you need to remember more generally.
Other people's annotations on the sheet music can be useful too. You might find helpful hints that people have worked out for how to play a particular trill, for example. However, be aware that old scribblings might not be relevant to your group's (or this particular) performance - don't trust someone else's markings that you're not doing the repeats, unless you know that's definitely true!
Obviously you have to read the music, but also read any instructions you've been sent/ given. Most groups communicate by email these days, or they might have a members web page with dates etc on. Read them. Reply if a reply is needed (and by the date you're asked to reply by). Ask about things you need to know that haven't been covered, but otherwise read, note down what you need to, and don't be that person texting the night before to ask if there's a rehearsal when you can check your emails/ the website/ your diary. Sometimes you'll be asked to fill in some sort of form (e.g. Doodle Poll) to conform your availability or attendance - unless you have some sort of technical difficulty doing this, then follow the instructions and fill in the poll (because if you don't, the person managing it then has to collate information from emails and texts and things people have said to them in passing, instead just seeing it all together in the poll... can you tell this one is a bit of a personal plea?!).
Extra musician bonus points are given for reading ABOUT the music you're playing - what do you know about it? Why was it written? What period of history is it from? How does this affect how it's played? This doesn't have to be extensive research in a library archive, even a quick glance through a Wikipedia article can help!
And to help you do all this... be prepared
Being prepared by practising goes without saying, I hope. But just in case it doesn't... if you have access to the music, then at least some level of familiarity of it is extremely helpful. It may be that your group does a lot of sight-reading (we do at flute choir, it's one of the aims to help people improve their sight-reading skills!), but if you're expected to practise outside rehearsals, then do. Don't be the person who is obviously only reading their part once a week (and yes, it is obvious), whilst everyone else is squeezing in five minutes a day and getting to know the piece.
For rehearsals - take a music stand - unless you're specifically told that you don't need to take a stand, you probably need to take a stand. Take your instrument(s). Take a pencil. Take your music - I've got a tray near my front door with all the music I'm currently working on, so if it's Tuesday and I'm going to orchestra rehearsal, I can grab the folder with my orchestra parts in. If you tend to forget things, write yourself a list and stick it to the front door and check you've got everything before you leave the house. If you think you'll forget to check the list, set a reminder on your phone for five minutes before you need to leave the house, to remind you to look at the list.
If you know that instructions are likely to come by email, check your emails regularly. It's all about getting into habits that make it easier for you to turn up and do a good job.
Flute player and teacher blogging about playing, learning, teaching and researching music.
The Reliable Musician - a series of blog posts on the skills that make the sort of musician people want to work with!