If you use Excel regularly, you should already know that you can see the sum of a group of cells by selecting them and looking in the bottom right of the Excel window. But if you actually want to enter a SUM formula, there's a handy keyboard shortcut to make it easier.
Helen Bradley (one of our favourite tech writers) notes that if you type Alt-=, the SUM function is automatically entered. OK, SUM isn't the hardest sequence to remember, but in a complex spreadsheet the time savings will add up.
This is joining my existing list of favourite Excel keyboard shortcuts, which already includes using Alt-Enter for a line break. I also learned another one from Helen's post: Control-' will copy the contents of the cell above the current cell.
5 Cool Excel 2010 tips and tricks [Helen Bradley]