When it comes to building citations, most local SEO's will either build them from a list, starting with aggregator's and move onto more niche local sites, or you can use a submission service to take care of this for you.
The pain point with local business citations begins when the business makes a change relating to Name, Address, Phone Number (NAP), removal of a service that affects their primary category or modifying opening hours. If you are not using a listing management service you have to log into each site and update the details.