The basic principle of any tile layout is that you want full tiles in the most visible areas of a room, and you hide cut tiles in less visible areas.
Generally, all of the horizontal grout lines should line up from wall-to-wall in a room. In figuring out the vertical grout lines, you should treat each wall, or section of wall, as a separate layout. This way you can choose the best layout for the visibility of each wall.
Making a Jury Stick
On walls you can't really lay out tile to see how they're going to fit. So it's a good idea to make what's called a jury stick or tile stick. Basically this is a straight piece of wood (a 1x2 works well) with the proper tile spacing marked on it.
To make a jury stick, lay your tile in a straight line on the floor using the proper spacing for your grout joints. Be sure to include any pattern or accent tile you will be using.
Mark the tile and grout joint spacing on the stick. If your tiles are square you'll only need one jury stick, but if your tiles are rectangular you'll need one for the horizontal layout and one for the vertical layout.
In some cases where both ends of a wall are visible you'll want your tile installation to be symmetrical. This may be the case for a back wall of a bathtub surround, a wall in a shower surround, or the back wall as you walk into a room.
For this type of layout, first find the center of that wall section and draw a vertical plumb line using a level.
Use the jury stick to mark the spacing of the tiles horizontally. Start with a grout joint on the center line and mark tile spacing to the end of the tile section. Do not fit the tiles tightly into the corners. Leave about a ¼” gap, which will be filled later with caulk.
You never want the last tile to be less than 1/2 the width of a full tile. If it is, adjust the center line 1/2 the width of a tile in either direction. This means instead of having the grout line at the center, you will have a full tile centered on your center line. Then draw a new vertical reference line where the grout joint of the center tile falls.
You may have walls where only one side is visible, and the other side is hid behind a door or fixture. In this case, you want to start with full tiles at the visible side and put cut tiles in the hidden corner.
First locate the most visible horizontal line in the room. Measure up from this point one tile's height and draw a level horizontal line. This is to ensure you have a full tile at the most visible line. (Don’t assume that the floor or tub or countertop is level. Use a true level line as the basis of your layout strategy.)
If you have a design or trim tiles that run horizontally along the walls, determine that height and use this as your starting reference line.
Use your jury stick to see how the tiles layout going up and down from this reference line. Be sure to to leave a consistent small gap above the edge of a bathtub, countertop or floor. Again, you don't want to cut any tile to less than half its size.
And check the floor, tub and counter for level. If they’re not level, make sure you can accommodate the slope by trimming up the bottoms of successive tiles as the tiles meet the tub or floor – instead of having to create slivers of tile to fill in below your full tiles.
If your top and bottom rows are also visible you may want to put full tiles there and hide the row of cut tiles in the middle where they will be less noticeable.
If you're only going up to a certain height on the wall, you can adjust this height a little to allow for more full tiles. For tub surrounds you don't go all the way up to the ceiling, usually only 42 inches from the floor. You can adjust this to allow for full size bull nose tiles at the top.
Surrounds for showers usually only go up about 6 feet. Again you can start with full tiles and end with full bull nose tiles. If you need to have some cut tile you can hide them in the middle of your layout.
At the bottom of a tile wall you may want to put in a special base tile. It's got a flared bottom to give you a nice transition between the walls and floor. It's nice to keep these as full tiles. Don't confuse these with a "sanitary base" tile which also has a finished top and is used in areas without wall tile.
And keep a close eye on where light switches and outlets will fall. Make sure that the electrical cover plate will fall either entire within the tile or entirely above it.
Laying Out Sections
Wall tile is most likely to have built-in spacers. So you can set one row directly on top of the one below it, and you can butt the tiles together side to side. This means that you will need less layout lines. Make sure you have enough to work in sections, so you don’t have to set an entire wall at one go.