For those not familiar with Excel, what's nice is if you put the cursor in a cell watch the command line. If numerical data appears, you can change it and watch all new results appear all over the table automatically (if a formula shows, leave it alone!).
I color-code the font in my charts to indicate which is the "master cell", where input is variable - the "slave cells" will reproduce this without prompting, and are colored differently. Output values are also coded for easy recognition.