There are a few other, interesting options in the Sprite Editor:

•  In the Slice dialog, you can set the Type to:
  • Automatic: Unity will try to automatically slice the sprite sheet into individual sprites.
  • Grid By Cell Size: Unity will slice the sprite sheet into a grid with defined size of every cell in pixels. You can slice the sprite sheet into 64 × 64 pixel cells for instance
  • Grid By Cell Count: Unity will slice the sprite sheet into a grid of sprites with the given number of cells and rows
• You can also set the Pivot of each sprite in the Slice dialog. There are multiple options available for setting the pivot of each created sprite to the center of the sprite, right corner, left corner, and so on.
• You can also trim each sprite manually when you select it. To do so, click on the border of the sprite and drag it.
• You can adjust the pivot of each sprite in a similar way. Select the sprite in the Sprite Editor, click on its pivot (the blue circle), and drag it to change its position.