I've plumbed the new basement shower drain and p-trap. I was assuming that I would have to backfill the hole and patch with concrete. I've seen information that seems to imply that its best just to backfill with sand and not patch the concrete. What is the best practice, and what is the recommended backfill material?
Also curious if there is a trick to determine the correct height to stub the pvc drain at?

Sand only can allow vermine to enter the structure. They will chew through just about anything that is not metal. As far as the height of the ABS, it depends on the shower you are installing. Get a drawing with diminsions from the manfacturer. Make sure you seal the ABS to the shower drain properly. Good luck.

when I don't have access to the shower drain from below, I just run the trap riser up higher than needed. use one of the shower drains that seals with a rubber donut from above. either do some careful measuring or just attach the drain to the shower, set the shower ontop, mark the riser, remove the shower, cut the pipe, put down a good mortar bed and set the shower for good.

I use sand and the cover the hole with Tyvek building wrap or plastic. I tape the covering to the pipe and the concrete. It's suppose to keep the radon from escaping thru the hole.