While some online forums give you the option of creating a business account, it’s a good idea to go into online forums from a personal account and let locals build relationships with you as an individual, not a faceless entity.
Before you start advertising directly, you’ll want to build up some good will with the community. Be consistent, posting 2-3 times a week. Ask questions, take polls, and provide valuable information specific to locals like answering homeowners’ questions or giving advice.
For example, if there’s going to be a huge winter storm, a plumber could post in these forums to let locals know, and tell them how to prepare so they don’t have to deal with issues like burst pipes. With a little bit of time and patience, people will start to get to know you, and you’ll be top of mind whenever they have an issue that requires your services. Then, once you’ve established good will, you can start to be a little more promotional, like letting locals know when you’re running deals or sharing special offers.
Facebook groups are an excellent way to find customers who are interested in your services. For example, as a plumbing company, you’re going to want to look for homeowner and home-improvement groups. You’ll also find HOAs on facebook, and can ask them for a recommendation, or for them to share your content. Your main focus however, should be on getting into local/county/neighborhood groups.