Hi Stepfun, I have found it helpful to have one on one chats with my DP, if I feel that DSS needs to be told how many beans make five.
Anything relating to basics like table manners when we are all eating our evening meal for example (please will you eat with your mouth closed), leaving lights on when not in the room, etc (please will you open the curtains so you can turn off the light), are just things I tend to say automatically, because they are generally a good thing to correct "on a case by case basis" and actually DSS laughs because DH gets told the same things.
For bigger things, discipline etc, homework, DH covers those (but often with me in the background mentioning something that may have passed DP by!)
The most important thing for DP and me to is have a united front. It has been very difficult to fully demarkate what I can and cannot do as a SM. It has definitely evolved over time, sometimes its trial and error and it has required infinite patience to talk stuff through and constantly ask for opinion and consultation. Largely our parenting style is in alignment, but I tend to be on the stricter side so have learned to pick my battles!
Perhaps I break all the MN rules by doing some of the things mentioned above, but the investment has meant we have a reasonably happy household. I have needed to keep up the constant communication piece as I was scared in the early days of overstepping the "invisible" mark of DSM.
IME, Young people /teens can be receptive but its a question of picking the right time/place - then mention just one thing to them (ie dont bombard them with multiple things at once). Yes, it makes the process a helluva lot slower, but better to "win the war" in 3 slow phases (eg get him/her to put clothes into the laundry basket, then sometime later get them to do that, plus turning off light, and so on until they become housetrained.... By the time you "nail it", they have left home, but hey ho!!
Caveat, this is only my experience, others will maybe tell it from a whole different perspective!