One of the beauties of DnD is the potential for actions to reap horrendous consequences. In a video game, you get to respawn. In real life, you would never risk your life to begin with. But DnD walks that fine line between long term consequences and still getting to play and have fun if your character dies. But, as a DM, how do you approach the deaths of your player's characters? Here are some tips and ways you can make those moments even more special.
PC Death is a Big Deal
To be frank, your players won't die very often. Even in a game, people tend to have decent self-preservation skills, and with action economy normally stacking in your party's favour, their deaths are by no means assured. Of course, as the DM, you have the ability to kill them at any time. However, keep in mind that death for a player's character is the end of their story, and as the protagonists of their own stories which you are merely the facilitator of, it's important to keep in mind that you're essentially killing off one of the main characters of the story your group is in the process of telling.
Deal with it After
There are two times that a PC is going to die: in combat or out of combat. If you're PC is going to die out of combat, it's a safe assumption that you and the player have talked about things before hand and are okay with how things are going to shake out. Don't execute your PCs with narration without them knowing it's going to happen. This is perfectly reasonable, and a great opportunity to use their death to further the story. That makes it uncomplicated. The complicated one is when a PC dies in combat, which is the more likely and common scenario. When a PC dies in combat it normally means they were fighting to stay alive, it means they don't want to die, and it means you probably don't have anything specific prepared for that particular character. Once they are dead, prepare something. Some time for a funeral, a nod from their passing soul, a favored trinket for someone to recover. Give the time to recognize that one of the characters has passed on, so that the players can see the gravity of their actions and the effects on the story. This doesn't need to take up much time in game, but it should take up some time around the table. It also gives weight to each character, no matter how small. If you rush through to the next action that's fine, but at some point come back and allow the party time to acknowledge what happened so that death doesn't feel like no big deal.
Ask not what you can do for death... wait...
Any time you're making conscious decisions about your world, you should take a second and ask yourself: why? Most of the time this has an easy answer. Why does my world have no gods? Because I want magic to be mysterious. Boom, easy. So, when you kill a character, ask yourself what purpose their death can serve for your story. Sometimes you can frame it to nicely set up the party for a revenge tale against the BBEG. Sometimes you can use it to highlight a particularly nasty betrayal by an NPC. Sometimes it can be used to hammer home the callousness of the party's actions. Don't let a character that has been slowly and surely fleshed out and developed simply pass beyond the veil without contributing some kind of change to the story you and your group are telling. Character makes story, so a character death changes your story.
Give Your Player Their Due
This person has been pretending to be this other person for quite some time. Even if they are ready to move on, it's still worth taking a moment and remembering all of the decisions and cool moments that have happened at the hands of the deceased PC. I find it works best when you highlight the decisions the player made to get them up to that point, either in a broad sense or a small one, so that the player feels as though they have accomplished something in getting their character to this point. Add a little personal touch so that the player doesn't feel like the death they would have experienced could have happened in exactly the same way to someone else. For instance, your Cleric who dies might get a send off from their god, whereas your rogue might get a nod to them simply stealthing away from their own body. Each player makes tons of decisions about their character, and those decisions effect the game that you all are playing. Give them credit for that.
Player character death has a lot to do with story, because when we boil DnD down to its essence, it's group storytelling. And your players act as the main characters. It's part of the reason we hate players who don't listen, because they aren't actively involved with the group story, and it's part of the reason why character death feels like such a big deal. Don't be afraid of killing your players -- I mean player characters -- but when you do be sure to give it the time and attention it deserves. And don't forget, killing a player character feels waaaaay better with a shiny new set of dice.