As a homeowner you go to the tile store and you find a tile you love and the price is right. You would think your job is done. If you're shopping at a place like Floor and Décor or  you have access to the stock of tile you are purchasing, we recommend you do a tile guy 'trick' that sales people at the tile store will not tell you. Take two tile and put them finish face to finish face. Look at the edges and see if they flare out. This phenomenon is called 'cupping' and when a tile cups it makes it next to impossible for us to get a perfectly flat, lip free install. That is why tile manufacturers will recommend not installing tile 50% offset (brickset) The middle of the tile is cupped high, the edges are cupped low and you will have a horrible lip at the junction of the three tiles. Below, I model two garbage tile that should never have been purchased. This information is invaluable to you because most won't even inform you of this problem. As you can see from the photo the middle of the two face to face tile is tight, while the edges flare out. If you care about a perfect finished product, be wary of what tile you buy! You get what you pay for and the saying couldn't be more true then when you are buying tile.