Depends on the child and situation. With dd1, I do a lot of the "Oops, whiny voice - try again." or the like... simple, non-engaging correction. With ds (my super sensitive soul whose emotional state is mirrored in his voice) I am finding it best to bend down, hold his shoulders/ hug him and tell him to relax this part of your body (while rubbing his chest) and ask him to use his strong voice. Telling him to simply try again often resulted in more frustration and desperation to be heard. This way, he takes a deep breath and says it again with a quiver, but no whine..
works for us.