I have seen many new users post many questions and they get answers for it... They often forget to mark the correct answers.... How to tell new users with 0% accept rate to improve it?
If at all, politely would be my keyword. Snarky comments about accept rates will often be removed. Personally I see this more as one of those "discovery" things (a bit like the badges) - so it'll happen automatically in many cases.
Until then, upvotes from other users go a long way to acknowledgement of a good answer.
I think it should depend on what acceptance rate they have. If a user has 0%, it's likely that they just don't know how SO works and didn't realize they have to accept an answer for previous question. In that case I usually post something like this:
@user: please revisit your previously asked questions and accept some answers. You can do this by clicking the check/tick mark to the left of the answer just below the votes. Other users are more likely to answer a question if they see a high acceptance rate.
If the accept rate is above 0% but below a certain amount, I usually write something like:
@user: please revisit your previously asked questions and accept some answers. You have currently marked x questions as answered out of a possible y.
I think it's best to stay polite, but sometimes you can't help yourself when a user has accepted 2 out of a possible 37 questions :-)
Mostly people leave comment suggesting to accept answers for other questions. I have seen it work in a few cases.
Other than that, if there is no compelling reason to accept answers, nothing will persuade them to do so.