What do you intend to achieve with this Product Hunt launch? Comments, upvotes, traffic. Establish those metrics first. With that in place here are 3 things that you may choose to do:
1. Your focus should be on the people not on the product. Emphasize how your product will affect the people because people care about their problem and not about your product until you tell them how your product is going to fit into their life.
2.Build your community and audience around your product and your brand well before your launch date.
3. Start working with the media and if possible influencers in advance of your product launch. Your product might not get a whole lot of coverage but the idea here is to ensure that you are not starting cold on launch day. If your budget allows, throw a Press Event for your product announcement.
@julia_demyanchuk Yes of course if those Facebook, Reddit groups allows such posts. Create some buzz before the launch with some anticipatory, "coming soon" content. Share teasers. Start some giveaways and contests to increase engagement. Most importantly your social media posts (Facebook, Twitter, Reddit etc) must have value, so that it will motivate people to share it and stay interested enough in the product