Guess You’re Neutral Evil Now!
Unlike many other DMs, I have always liked the alignment system in my D&D games. Certainly I have seen DMs use it incorrectly and have come across as heavy-handed, but it has always served a few key purposes for me. Similarly, back story for each character is something I require, though there are no rules that state it is mandatory. 5th edition has done an amazing job incorporating them through the use of backgrounds, and custom backgrounds are incredibly easy to make. Here are the reasons and ways I use these.
First, I like when alignment is used to help a new roleplayer understand their character when making decisions. It can be daunting for someone to suddenly have to decide what their character is doing when they haven’t really been playing all that long. In these cases I can point to their alignment and explain what they might do if they want to be consistent to their previous ideals. I do NOT force a player to adhere to alignment, but in their early games I will suggest it as a guide. This makes it more accessible. “If you’re not sure how your paladin would want to enter this boarded up house in the city, consider your Lawful Good alignment. Likely he will either track down the owner or guards first for permission. If time does not allow, perhaps tear down the boards, but return later to replace or repair the damage you caused.”
Second, I love to use alignment as a peculiar feature of magic since only certain spells incorporate it. Spells like Protection from Good or Detect Evil directly relate to someone’s alignment, even though someone’s alignment can be ever-shifting. This makes for really interesting story; does your character want to steal all the noble’s food because they hope to distribute it to the poor? Better not run into any paladins along the way who will instantly see your now evil alignment! You would think that this abandoned town doesn’t have laws, but it technically falls under the king’s lands, and so by ransacking the buildings you now have a chaotic alignment! I once had the players enter a city where the regular citizens were protesting paladins and their at-will use of Detect Evil, claiming it was an invasion of privacy, and not a fair depiction of their morality as people.
Backstory is another feature that I feel is a quick and easy way for a player to figure out how to make choices in the game. By understanding their motivation and history, they can be consistent, or weigh their new directions against the whole picture. The main thing to remember though is to never prevent your player from making a decision; you can point to their alignment or backstory to question their motivation, but don’t say “you wouldn’t do that.” and shut them down. It is not asking too much that a player only jump into the game when they have an idea about who their character has been up until the start of the game. There’s not a lot of stuff I force my players to do, but choosing an alignment and backstory are both things I absolutely require.