Mac Excel (in Microsoft Office) -- increase numbers +1 by dragging

You just need to do the following:

1. Highlight a cell 
2. Move your curse to the lower right hand corner so that the curser will change to a "cross" with dark in colour
3. Move the curser down by dragging the cell with  "alt/option" key on hold
4. Next cell will have a value increased by one from previous value.