Tile Laying - Preparing The Surface Step 1 is to prepare the surface that you'll be laying the tile down on.  If you're laying tile on a wall most likely you don't have to worry about the surface being flat, but laying tile on a floor, you do.  In contrast, when laying tile on a wall you have other things to worry about, like the tiles falling off. Either way the first step is to clear your surface.  This means scraping off crud and build up if there is any, or removing or hammering in nails, etc.  We want as smooth as a surface as possible for the tile to go down on so we can a smooth surface of perfectly laid tile.  After the surface has been leveled, clean it with a cleaner to degrease any sort of substance that would inhibit the cement from sticking to the base surface. Next, we need to see how level the surface is.  Again, if you're putting tile on a wall you shouldn't have much of an issue here, and also because you're probably not going to bother with fixing a wall from being straight.  But the floor you can fix.  Measure your floor with a level to see if you have a nice and flat surface.  If you have a slight dip in certain places you may be able to fix smaller issues with a few easy techniques.  If you surface is just simply old and not very smooth you may need to lay down a base layer of plywood. If you're laying a new floor of plywood place your nails about every 4 four inches apart or so around each panel of plywood and make sure the nails are flush with the plywood or slightly recessed. If you've corrected a few sinkholes in the floor, now's the time to double check to see if you're floor is nice and level.