Joining organisations like the local Chamber of Commerce and FSB groups will help, but like anything you will need to put effort into establishing yourselves at these groups as you will be one of many.
The Chamber will have smaller or small businesses, and it may take a while to get known in the room. The FSB is going to be micro businesses and trades, so to be honest probably unlikely to work for you.
If you are lucky enough to get into a local BNI group than in your line of work that would work well for you, if you can work to their rules and play the game. The problem you will have is that your market is very crowded and you'll find it difficult to find a group with a gap in your sector (as it's exclusive only).
Depending on your area, you may find the IoD run some events in your area. They are usually medium to larger businesses, and if you work the room and build relationships there you may find a larger and more sustainable client.
You should find some local business publications and get on their mailing list, as these usually have a list of local networking groups published in them. If not, then joining your local Chamber of Commerce and then ask them, they should be able to help give you a list.