When laying tile, here's an easy way to save some time before applying any mortar. Dry-fit the tiles on the surface you're working with. Next, mark any pieces that will need to be cut. That will help you determine how to get the best design and fit, and doing so will enable you to avoid the mess of pulling up the tiles after the mortar's applied.
For more on tile, consider:
How To: Install Tile
Laying Glazed Ceramic Floor Tiles (VIDEO)