Chores & significant (age appropriate) contribution to the running of the household. They're not helping their parents out, they're doing what they should do because everyone puts in what they can to get the best possible for everyone. Kids are not the royalty of the house, they don't need to be waited on if they can do something themselves & being given responsibility makes you feel capable. Plus if you're used to hard work you won't be so scared by the prospect of it at 18 or whenever you move out. 'De chacun selon ses facultés....' 
My ex grew up with a household of staff and then later was at boarding school and he had to l.e.a.r.n. (slow fucking process) how to do everything - I fell into the trap of doing everything for him before I realised how not on it was.
My mum, while in a v. happy marriage, also grew up with maids/cooks and she'll leave the kitchen looking like a bombsite after making breakfast etc, expecting my dad to clear up, which I think if he didn't find it funny in a resigned sort of way could become a bone of contention. It was with me when I lived with them anyway!
Even if I do have staff (and kids!) growing up I still think it's vital to teach them what needs to happen to maintain the smooth running of day to day life & to give them hands on experience of this. Of course it's easier not to bother teaching them but that's doing them and future partners a huge disservice IMO (and IME!).
Def agree re: needing to learn how to vocalise feelings and communicate in an emotionally literate way although of course for some it's much easier than for others (alexithymia?).
I also do think it's good for both parties if you know how to be 'quietly confident', as in happy to be assertive without being forceful about it, and feeling comfortable with drawing and keeping boundaries.
And affection (if that's your bag), little kindnesses and thoughtfulness.
good thread :)