Asking vs Nagging

Since so many of you are wives and partners, and the housekeepers and domestic goddesses of your abode, I wanted to pose a question. 

I'm a pretty neat and organized person. I'm also somewhat clean, but not twitchy about it.

Almost everyone I have ever lived with has been much more relaxed about cleaning than I am. 
As in, they don't take initiative to clean a space until it's causing issues (like animals are getting into the dirty dishes laying around the house). 

I tend to fall into this rut where I become their mom, cleaning up after everyone who make make vague promises to clean but have no follow through, which then sets a precedent.

So my question is this:

How do you get your partner to be more proactive about cleaning up after themselves, without being a nag, implying they're being a slob, having to ride them about it for weeks, etc? 

Ultimately, I'd love to only be having to do HALF the cleaning of the house, with him doing the other half, as it seems fair. But clearly, having a clean home is a different priority for us.

Any advice is GREATLY appreciated!