We usually kill off the grass first by covering with heavy cardboard and leaves and leaving it all winter, in the spring pull out the cardboard, add bags of top soil some peat and sand to the decayed leaves and mix well together, we usually add other amendments such as blood meal, bone meal, phosphate, according to instructions. To have a good loose organic soil with good drainage is the the objective. A raised bed decreases need to bend or kneel. Good luck.

So, I'm curious... will 12"-16" of soil placed over the existing grass be enough to kill it off? I'm asking because I am thinking of making a raised bed or two in the next few weeks but am unsure what to do about the grass below. Should I place a thick layer or newspaper over the grass then set the soil above that? Will the grass be able to find it's way through the classifieds and 12"-16" of soil to the sun?

Put the newspapers or cardboard down just to be safe. If the soil doesn't kill the grass you will be so sorry.