I can only speak for what I do. Don't have a clue whether it is the best solution or not, but here it is.
In the past I've used two methods.
The first method is if I am not in a great hurry to use the plot. In that case the new bed gets covered with black plastic or other heavy tarp (when the grass is actively growing) and a few weeks are allowed to pass before the tarp is removed and the area is plowed under with a tiller. This is by far the best way IMO because the grass is almost 100% killed and does not cause any problem in the beds.
The second method turns out to be much more labor intensive. In this method the bed gets plowed, and loose grass is raked out and tossed into the compost bin. About two weeks are allowed to pass, and then the area is tilled a second time. Loose grass is again raked out. At this point the area is ready to be used, but there will still be a fair amount of grass to survive and so effort is required to hoe or otherwise remove any grass that is trying to survive in the garden spot.
I do not like the idea of cutting the sod out and exporting all of that top soil from the area. I also do not like the use of herbicides to kill the grass.