I'd go with one of the social media monitoring tools available on the market. I tend to be biased when it comes to such questions, and I'd recommend having a look at Brand24. Here are a couple of tips for starters:
-add your competitors’ names as monitored keywords
-monitor their domains as some people tend to include the domains rather than social media handles in their
-monitoring branded hashtags is worth considering, too.
Sentiment filter can be a super helpful feature as it allows for filtering the mentions according to people’s attitude expressed in their posts. With that being said, you can easily get to those mentions from people dissatisfied with your competitors’ services or products.
I see people looking for help or asking questions on social media that some brands do not bother to reply to, and you can find hundreds of such posts with a social media monitoring tool. If you're capable of helping those people, there’s nothing wrong in jumping in such conversations. Someone else’s negligence might actually turn out a win for you.