I do as others have described... with that said, I know the call takers and dispatchers must follow EMD procedures, and don't want to force them to break their workflow or be dinged in compliance. With that said, I'm familiar enough with MPDS that I prompt in the order of their questions. Unless in my own district, I see no reason to identify myself, but hope the calm, confidence and organization of my call lends the call taker to trust my report. I'd rather earn the respect than demand it.
I learned this the hard way a few years ago, when calling in a bicyclist struck outside my district. I knew all the relevant information to say, and gave it all, but it was in an order that was not useful for the call taker and was inadvertently labeled as a difficult caller - and could hear the frustration at the other end of the line. As soon as I shut up and let them direct the conversation, everything went smoothly. That delayed the call and activation of resources.
Around where I work, we have exceptional call takers and dispatchers-- just like we get frustrated when given incomplete or seeming contradictory information by the "voice in the black box", they are limited by the information they can access-- and are only as efficient as their procedures. I know dispatch undergoes as much (if not significantly more!) continuous quality assurance as I do in the field, and have confidence in the systems to work with the goal of optimizing care.