I don’t know if it needs saying, but getting a good quality one is the key. Cheap ones are noisy, wasteful, not durable, and do a poor job - to the point of having to partly wash your dishes before you wash them in the dishwasher. A good quality dishwasher will last, be quiet, and handle some pretty dirty stuff. That said, even commercial kitchen dishwashers don’t take everything off, so have some realistic expectations.