Here are some things I try to do BEFORE the first rehearsal:
When you get your pianist a copy of the score, reserve one for yourself. Spend at least some time practicing from the piano score, reading the bassoon part. Your eye will wander down the page and you'll see what's going on while you're playing. Spend some time with the score without the bassoon. Copy helpful piano cues into the bassoon part. If you have some piano skill, play some of it to hear what the harmonies sound like.
Prepare for the first rehearsal like a conductor. Think about where cues and prep beats are helpful. Craft the beginnings of an interpretation. Notice where the nuances are in the music (ritard, rubato, places where the time is flexible, etc.) and practice showing them in your playing before you get with the pianist. Be responsible for cut-offs and silences.
In the first read-through, along with having all the notes in place, try to show dynamics, tempo changes, style very clearly. I make a habit of almost over-doing these things so the pianist becomes especially attentive to your interpretation. Pianists who accompany a lot are very solid players and will tend to take over if they don't feel real authority coming from you. There is nothing wrong with this on its face, except that you may not always agree with what's being done. You've worked much longer on the piece than they have and know it better (it's assumed!), so don't throw away all that study and play passively.
After the run-through, go back and work on things together. Slow metronome work is helpful in places so both can see how things fit together. Keep the pencils handy! I always add more cues to my part after the first reading! Work on anything either of you doesn't understand until it's very clear what to do.
Talk about your goals for the piece. Some parts may not be up to tempo yet. What is your goal tempo? Is it realistic for the pianist in the time allowed? What style or colors do you want to bring out? What effect should the piece have on the listener?
Finally, get the schedules out and work backwards from the recital/concert to block out rehearsal time.