You can make a worksheet more efficient by providing drop-down lists. Someone using your worksheet clicks an arrow, and then clicks an entry in the list.
Select the cells that you want to contain the lists.
On the ribbon, click Data > Data Validation.
In the dialog, set Allowto List.
Click in Source, type the text or numbers (separated by commas, for a comma-delimited list) you want in your drop down list, and click OK.