Design in Blocks
One of the more important considerations when attempting to create a well designed spreadsheet model is the concept of designing in blocks.
“Blocks” is a colloquial rather than a technical term, and means a “range of contiguous cells that have something in common”. This could be something trivial like number format (currency, percentages, etc.), cell shading, and the like. Or it could be something more meaningful like a logically identical formula.
One of the benefits of designing in blocks is that it becomes easier to see where areas of your model start and stop. It is also then easier to add new rows or columns to the block. Furthermore, it becomes much easier to navigate through your model, especially if you use keyboard shortcuts like Ctrl and arrow keys.
But possibly the greatest benefit comes when writing formulae that refer to the block. In this case, including the blank row/column at the start and blank row/column at the end of the block will ensure that new rows or columns added to the block later will always be included in the formula.
In this example, you can see that the total formula in cell D10 refers to the block of items above. Importantly, it includes the blank row at the start of the block (row 3), and the blank row at the end of the block (row 9). This means that when a new row is added at the start or end of the block it will be included in the total formula.