DOI for a yet-unpublished paper Suppose I have a paper #1 which was accepted by a Very Respectable Journal, and has been assigned a DOI, but has yet to be actually published (i.e. it's in the queue, and the DOI is not "activated", so it doesn't work for now).

Suppose, at this point, that I write another paper #2 in which I cite paper #1, saying that it is accepted by Ver. Resp. J. In this case, should I or should I not provide the DOI?

The possible downside of this is that someone may try to use the DOI before it goes live and be confused. On the other hand, if someone reads the version of paper #2 later on, the DOI may be more helpful than mere mention of the paper being accepted at Ver. Resp. J.
Assuming the formatting requirements of your journal say to include DOIs, I would do so. One of two scenarios seems most likely:


Paper #1 will appear in press (or online) before Paper #2 is published, at which point it is a trivial edit to change the in press citation to the proper published citation, with the DOI.
For some reason this doesn't happen, and Paper #2 sees the light of day before the DOI in Paper #1 goes live. For a relatively short span of Paper #2's life, readers won't be able to get to the DOI for paper one - but for what is likely the majority of the paper's useful life, the DOI given in the references section will be live, and will point to the published Paper #1.


It's only in that really brief span of time where a reader might try to access the DOI and not be able to. I think optimizing for that time (which may be zero) is counter-productive when you view a paper over its entire lifetime. At best, you have what is essentially an auto-updating reference. At worst, a reader goes "That's odd..." and emails you to see if they can get a preprint.