It doesn't count for as much if the paper isn't yet accepted. You can list it on a resume with the title, authors, etc, and at least they can tell that it's been written. I would make sure you put the submission date though, and it should be close to the present date.
My resume has pubs, accepted papers, and after that submitted papers with date.
No. Nothing is as good as being able to list a citation, though it's close if you've been notified that a paper has been peer-reviewed and accepted for publication and will appear in a journal in a given edition.
It's considered acceptable to cite accepted papers.
You usually do it like this if the publication is accepted but not online yet:
Duck, D., Mouse, M., Pooh, W., et al "Adventures in the Magic Kingdom" American Journal of Cartoons 2010 (in press)
Like this, if it's in epub but the publication date hasn't been determined yet:
Duck, D., Mouse, M., Pooh, W., et al "Adventures in the Magic Kingdom" American Journal of Cartoons 2010 (e-pub ahead of press)
and obviously once you know the pub date:
Duck, D., Mouse, M., Pooh, W., et al "Adventures in the Magic Kingdom" American Journal of Cartoons 2010 6
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