Shadowing what kind of medical professional?

Besides MDs, I know I can shadow DOs. But does shadowing NPs, PAs, or NDs count? Any other acronyms? (I tried to search the forums, but I couldn't find an answer.) While we're here, I'll ask a few more: how many hours are appropriate to ask for from a doctor you aren't already acquainted with? Can a doctor you've shadowed under write a LOR?
Source: Student Doctor Network - Category: Universities & Medical Training Authors: Source Type: forums