Ceramic tile: laying sequence?

Been a while since I've done this and I've forgotten this bit: Tiling a shower stall, 2" ceramic tiles (12 x 12 bonded sheets) over cement board and custom morter pan.
What's the sequence? Floor first, then walls, or walls first?
If floor first, how to protect it while doing the walls? Don't want to scratch the new tile with my size 12s or let thinset fall into the grout channels.
-Frank
--
(email: change out to in)

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

walls first, for that reason.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.