To build a shower pan for tile, install the bottom piece of the drain onto the floor, install wood planks to create a shower floor frame, place a rubber membrane over the frame, and attach it in place with nails. Make a hole in the membrane just above the drain, and install the second part of the drain to be about 1 1/4 inches above the membrane surface. Pour the concrete onto the membrane, and leave it to dry.
Before beginning to build the pan, make sure that the floor is strong enough for the concrete pan, and install exterior grade plywood for extra support if needed. Use PVC cement to install both parts of a PVC drain. For drains made of other materials, use PVC connectors. Find out the local building code guidelines on shower pan thickness, and make sure that the shower frame is deep enough. Attach enough rubber membrane to overlap the edges of the form by 10 inches, and make sure that the membrane covers all the surface where the concrete is going to be.
Nail the membrane in place at least 8 inches above the floor. Before pouring concrete into the pan, cover the drain with plastic and duct tape. To make a fully functional shower pan, the concrete on the outer edges of the pan should be about 2 1/2 inches high and about 1 1/4 inches high around the drain.