Keep the Count of the Rows and Columns involved ALWAYS on hand
If I want to sum 300 rows, I write: =Sum(M30:M330), I often can't remember the COUNT. Have I just summed 300 rows in that equation, or have I summed 301 rows? You see!? I WASTE A LOT OF TIME double checking that the area selected by my formulas selected the number of rows I intended or 1 row too much/too few.
It's hard to figure this out! It shouldn't be.
When I'm double clicked on the cell with a sum function, for example, highlighting a range of (M30:M330) within the function, I SHOULD BE ABLE TO SCROLL OVER TO THE BLUE BOX SHOWING THOSE ROWS HIGHLIGHTED AND AS I HOVER OVER THE BLUE BOX MY FUNCTION IS REFERRING TO, THE ROW AND COLUMN COUNT SHOULD APPEAR INSTANTLY SOMEWHERE CLEAR AND SAY 300R,1C , meaning "there are 300 rows and 1 column highlighted by this bluebox.
This would SAVE ME SO MUCH TIME AND EFFORT!