What do you think makes a good RP server?

Hello!
I am currently working on a GMOD RP server, I won't go too deep into what the RP is about as it's still in early development,
But all you need to know is that it's a DarkRP modification.

I've read so many articles/threads about people complaining about DarkRP and what it's become and I don't want to fall in the same category as those servers,

What do you think would make a truly enjoyable DarkRP experience? What are the things I should avoid?