Before your start laying your tiles, make sure that your floor is clean and dry. When you are tiling always try to avoid making small cuts in the tiles and in wet areas like your bathroom and laundry make sure you keep the fall, so that the water drains away. 

It’s a good idea to lay out some tiles dry, to see what the finished floor will look like. Before applying the adhesive, lay out the tiles on the floor using your datum line as a reference. Check that they are evenly spaced on every side of the wall. If they’re not, you will need to adjust your datum line.

In this case we need to cut a square in the tile for drainage. To do this, lay the edge of the tile you need to cut against the one that is laid next to the drainage hole. Mark on the tile along one edge the length of the drain. Then turn the tile on its side, hold it against the tile above and mark the width of the drain. Draw lines across the tile to mark the length and width of the drainage hole. Now in a well-ventilated area, use your angle grinder to cut out the square for the drain. Once you have cut the outline of the drain, cut a diagonal line across the square to make it easier to push the off-cut out. Lay the cut tile over the drainage hole.

Continue marking, cutting and laying tiles to fill the floor space. Use a straight edge or level to make sure all the tiles are lying flat or have the necessary fall to let water drain away. If any tiles are above or below the level of ones next to them, remove them and either add or take away adhesive to make them level. Use a damp sponge to wipe off any excess adhesive that may rise up between the tiles when you press them down.