Whenever a civilian is selected you will see a white flashing outline around him, and his picture will be shown in the toolbar.
As you move your cursor across the map it will alter according to what will happen if you click in that location. You can safely experiment because any order you give can be canceled at no cost.
Once you give an order to a civilian a yellow question mark will appear when you place the cursor over the ordered unit. Click on the unit and a dialog box informs you what he is doing and lets you cancel or confirm his orders.
You can be sure a civilian is working when the unit animates.
