With tiling it is often hard to tell the difference between an average tile installer and a true professional, the real differences are not what you see with the finished product but what is lies underneath.  The prep work for a full shower system is the most critical part and determines whether or not a shower will fail, installers who use shortcuts might be cheaper up front but will cost you thousands more down the road if you end up with a shower that leaks or worse.  That's why I form my mud beds by hand with a pre slope and final slope with a pan liner in between the layers.  By code a 1/4" pitch per foot is required.  Once I have formed the mud bed with a pan liner and put water resistant board on the walls, I use a waterproof liquid membrane to coat the entire shower from floor to ceiling.  This is a process a lot of installers skip out of laziness or just trying to be the lowest price, but it is a crucial step that is well worth it!   In the pictures below are some examples of the installation of the pan liner, a finished mud bed with a 2x4 and 2x6 used to form the curb and what the liquid waterproofing membrane looks like after numerous coats have been applied.