One bite at a time.
I’ve always loved this old joke, because it’s so applicable to any sizable project. And it’s especially true for any data clean up project.
Databases are never 100% accurate. People die, people move, errors get made. That means we’ve got to continually work to keep data up-to-date and accurate.
Most associations, when they consider the prospect of cleaning their database, become overwhelmed and decide to do nothing. But just like eating an elephant, the only way you can attack your database and clean it up is to take it one bite at a time.
So pick something simple (say, only current members or only volunteers) and start working on that. When you’re done with that subset of data, move on to another. Pretty soon you’ll find that you’re halfway through the elephant!