I don't know very much about how this works in practice in, say, the United States.
Roughly, my understanding is that there are party-appointed arbitrators and list-appointed arbitrators. But I don't know, for example, how list-appointed arbitrators get or stay on the list.
What are the best books to read to learn about arbitration in theory and practice? What are interesting real-life arbitration cases? Is it truly always the case that the arbitrator is neutral? It seems to be that an employer chooses to put arbitration in their contracts, for example, in part because the employer has greater power to choose an arbitrator whose views match their own.