Everyone knows you can copy and paste cells in Excel, but a lot of times you want to do it quickly in a specific way. Turns out there are two simple keyboard shortcuts that let you copy cells quickly.
Move your cursor to a cell that you want to copy. Suppose you want to copy it down five times. Hit Shift+Down Arrow four times to select the four cells below your current one. Then press Ctrl+D. Whatever is in the first cell is copied to fill the remaining cells. (Whatever was in those cells is overwitten.)
You can do the same thing to the right with Shift+Right Arrow and Ctrl+R.