I'm converting this old AD&D adventure (several of them, actually) for an upcoming 5e game. And one I really want to run basically spells out that:
*Only Good, heroic characters need apply.
*Their motivation should be to help the NPC's and do the right thing.
*They don't lie, cheat, steal, or attempt to barter for a better reward.
Now, that's pretty much how I play- even if I'm not strictly Good-aligned, I generally feel helping communities is important and showing compassion for others. But the whole time I'm writing it, I'm thinking "what if one of my players decides this isn't what they would do?".
Sure, there's the fact that if they don't want to go on the adventure, I don't have a game session for them, and yes, one should generally play characters that want to adventure, but at the same time, it's a roleplaying game, and you shouldn't have to be Dudley Do Right to go on an adventure!
I've had to grin and bear my reservations about situations that seemed hinky to me in the past, because otherwise, we wouldn't be playing at all. Heck, just recently, this NPC we encountered was all "there's an evil that must be dealt with, but I will help you do it", and something about the lack of information he was giving us seemed very suspect. But when I tried to ask questions, he just got annoyed and said "take my help or leave it."
So, frustrated, I said fine, let's do it. Cue the next session: "thank you for helping me achieve my evil goals, you fools!". /sigh