Multiple Cells, Same Data
For some reason, you may have to write the same thing over and over again in cells in a worksheet. That's excruciating. Just click the entire set of cells, either by dragging your cursor, or by holding the Ctrl key as you click each one. Type it on the last cell, then hit Ctrl+Enter (not Enter alone)—what you typed goes into each cell selected.
This also works with formulas, and will change the cell references to work with whatever row/column the other cells are in.