Most 'hacks' are noise, but a few things genuinely move engagement:
Reply to every single comment in the first hour. The algorithm reads early engagement as a signal to push the post wider. If you're posting and walking away, you're leaving reach on the table.
Hook in the first 3 seconds for video, first line for text posts. Most people lose viewers because they 'warm up' before getting to the point. Cut the warm up.
Post when your audience is actually online, not when generic stat sites tell you to. Check your own analytics and find your top 3 windows.
Carousel posts get more saves than single images. Saves are the strongest engagement signal on most platforms right now. If you have something teachable, turn it into a carousel.
The boring stuff (commenting on your own video, putting Reels in stories) helps marginally but it won't save bad content. Spending 80% of your effort on the post itself and 20% on distribution tricks is the right ratio.