When you start corresponding with a beit din (whether to ask for an application or after submitting your application), you will generally be talking to the Av Beit Din. So what is he and what does he do?
Av Beit Din translates roughly as head of the beit din. Av generally means father.
Depending on how big or small the beit din is, the Av Beit Din is generally the rabbi who oversees the program and its practical details. He is your contact person, the one you will email with questions or concerns. Your Av Beit Din could be different from your friend's even if you're using the same beit din, but that is unusual.
He may be paid and working in an official, full-time position. He might work part-time. The beit din may have a support staff or there may have a rabbinic intern or it might just be this rabbi. He might even be a volunteer, doing this in addition to a pulpit position or other full-time position.
He will usually not be the "highest ranking" rabbi on "your" personal beit din. Usually, at least one rabbi with "name recognition" will be included on your personal beit din because that's how our society works unfortunately. Ugh, that was a lot of air quotes. Bear with me here.
Overseeing conversions is generally not seen as a "sexy" field that the community appreciates, and it takes a ton of time and energy that could be spent publishing papers or giving talks. Appreciate the professional recognition that your Av Beit Din may be foregoing by choosing to work with conversion candidates. Even better, it's often thankless work that opens him to criticism if a convert or candidate goes off the rails. Who do people criticize first? The gatekeeper, who also happened to have the most contact with the person.
Of course, none of this guarantees he will be warm and fuzzy and fun to hang out with. You may not even like him. But you don't have to like him. Really. That sounds depressing, but it's actually a very freeing thought: if you aren't best friends, that doesn't reflect on who you are as a conversion candidate or as a Jew. This is essentially a business relationship. (Likewise, remember that this is a business relationship when you feel the need to overshare with your rabbi. That's not your relationship; avoid TMI when possible.)
Generally, you should not take matters over his head. If you like another rabbi on your beit din better, I'm sorry, but you should still keep the Av Beit Din assigned to you as your point of contact. That's his role in this process. The information will go to him anyway, so by involving a second rabbi involved with the beit din, you're making more work for everyone involved. Unless you have a really good reason, stick to the Av Beit Din when you have official business for the beit din. Of course, if there is a serious problem with the Av Beit Din or the beit din as a whole, find out who you need to talk to instead. (Easier said than done, I know. We'll talk about that another day.) Very few problems are that serious, and most of the ones that are involve potentially illegal and definitely unethical conduct. I'm not talking about a personality clash or "that was unfair."
Hopefully your relationship with the Av Beit Din will be a source of strength and positivity to you. But don't get upset if it's not. Keep your eye on the prize.
Can you think of anything I forgot?