When installing a new, tile ready shower pan, should a shower pan membrane be layed first? The manufacturer does not mention this requirement in their instructions. The shower pan itself is adhered with construction adhesive, rather than a mortar bed, so I would be afixing the pan to the membrane itself rather to the underlayment. Also, when a membrane is used, how is it afixed to the drain itself to direct the water into the drain?

I want to do this right the first time!