If the tub is level start with a full tile at its rim.
How to install ceramic wall tile around a bathtub.
Check if you need to adjust this mark to avoid laying slivers of tile at the top and bottom.
Then apply a generous amount of thin set to the bottom bathtub tile and position it 1 8 in.
Apply it to the wall with the bottom edge about 1 4 in.
For a tub surround only install the backerboard and tile 12 inches above the tub.
Follow the order shown in the diagram to snap the rest of the lines.
Fill the gap between the tile and the tub with caulk.
I cover some of the specifics of how to layout and set up a tub to install tile around it.
The best approach when installing cement board or other tile backer around a tub is to keep the cement board out of the lip area.
This video will show you how to set tile around a tub.
When tiling around a tub mark the first layout line at the vertical edge of the tile next to the tub.
To tile around a tub or shower start by measuring the height of the back wall from the lip of the tub to the top of the area to be tiled.