I try to keep things very simple. I'm very leery of giving the impression that my players' PHBs are useless or outdated, as well as causing confusion when they forgot about some minor rule that I added. So if I houserule something, I tend to just straight up remove it, rather than alter it, as that is easier for everyone involved.
I don't allow Great Weapon Master, Sharpshooter, or multiclassing as character options. Any race nominally 'evil' or 'monstrous', (Kobolds, Orcs, Duergar, Drow, etc) are probably off the table, unless I hear something super convincing, or they actually make sense for the setting or campaign theme. So Drow would be fine in OotA, not so much in SKT.
All other options from published books are fine, however, and I'm open to material from DM's Guild or homebrew sources, with the proviso that the player actually be the one to find and purchase the file themselves. I'm not going to collect material for them, but I will faithfully examine anything that they themselves find, if that makes sense.
More minor tweaks:
- No death from losing total+remaining HP in one hit; I didn't like how it only affected low level characters.
- Spirit Guardians affects bad guys when it is first cast, contra the errata. I don't apply the same logic everywhere though, since the more widely it is applied the more problematic it becomes.
- I'm a bit unsure of how magic items are meant to work with class abilities, but for the moment I've ruled that they cannot use Evocation or Life Cleric abilities on spells coming out of wands and whatnot. Might reverse this though, it feels more petty than anything else.
- Natural 1s and 20s always fail/pass, regardless of the roll type; if I'm not willing to let the player pass or fail even at that rate, I just don't let them roll.