As DMs we are trying our best to give our players a great experience at the table. Players are willing participants in this, but sometimes they need a little help. As DMs part of the job description is helping our players become engaged and immersed in the world we're creating. What follows are a few hacks to getting your players more engaged in the game. As anything, these are just some tips, they're things to try at the table to help your players engage, but as with anything, mileage will vary.
1. Use Your Player's Imagination
This is a valuable hack for any DM. We deal with so much at the table, sometimes our minds are incredibly overloaded with everything going on. So this tip is not only to help you engage your players more, but ease your mental load: that's a win-win!
Ask your players to describe how their character kills something, does a wonderous deed, or what their spells look like helps carry some of your cognitive load. But it also engages the player's imagination, which gets a player to invest in the world and story that is getting told. It's applying the IKEA effect to DnD, where we are much more satisfied with something we feel we've partially created.
Players are here to be apart of what's happening, not to watch a story unfold like a movie, giving players narrative control is powerful and may surprise you where it leads. A player's active imagination captures and engages them FAR more than we ever could. You may even experiment with some mechanics that allow for this kind of narrative control, but you may need to prep your table before you put the ball in their court.
Other systems like Ten Candles have this handing off of narrative control baked into the system. DnD is not quite as forward about this player engagement. It's up to you as a DM to control how much your players get this narrative control.
2. Let your Players use their cool abilities
DnD as a system has certain premises as its foundation. One premise most central is that this game is heroic fantasy. You can see this throughout the core rule books, specifically character creation where players are told about all the awesome stuff their characters can do. So you should try to design encounters that highlight those specific abilities, shoot for at least one cool moment for each character in a session. Try to make it something that only their character could do, because of their specific abilities.
Give a druid a creature they can talk to, or try to tame, or have druidic messages written in the forest. Give a wizard an ancient spellbook they need to decode, or a mass of monsters they can obliterate with fireball. Give a fighter a feat of strength they need to overcome. Or a rogue a chance to go on a stealth mission.
3. Give Your Players Mysteries (Questions & Answers)
Sly Flourish calls this secrets and clues, and I think is critical to any engaging game. You should always have 5-10 bits of information which move the plot along and points your players in the right direction. But to hone in on this further, I think that there are really two types of secrets and clues, and I'll call them Questions and Answers. Questions are clues that only give partial or confounding information. Answers satisfy previously raised questions by providing more, clearer information on what's happening.
Why only give partial information? Because people love mysteries. Even if we aren't in a mystery genre, this cadence of information naturally peaks our interest. A good example of questions would be: 1) The evil overlord is collecting bodies. 2) The evil overlord hands out blood-red platinum for these bodies. 3) The evil overlord's tower is GROWING. (btw all these are stolen from Matt Colville's Bad Guy's video.) This pulls your players along to want to answer these questions. It gives them a reason to play the next session, because they want these questions answered.
The answers could be something like 1) He is using the bodies to grow his tower in order to summon an evil god. 2) The blood-red platinum allows the evil overlord to track where dead bodies are. 3) His tower IS the bodies themselves. As you hand these bits of information out, you give your players a sense of progress. Progress is very good, players like to feel like they're progressing, not just in level, but in the story itself. I guarantee that good questions and answers will engage your players like nothing else will.
Honestly, I think Questions and Answers, and how you make them deserve there own in-depth post, but for now there you go.
One final thought to player engagement, is your own engagement. Players see and experience the world your create through you. So use things that you are passionate about, things that engage you, it's bound to boil over to your players. All the best and game on!