What to look for during a walkthrough?

In doing the walkthrough, you try to tell a story about why the user would select each action (in the list of correct actions), and how she would perform that action.
Throughout the story you should ask the following four questions:
  1. Is the effect of the next action really what the user will try to produce next?
  2. Will the user see the control (button, menu, light, etc.) for the action?
    An "ugly" control may be hidden so the user does not see it, let alone be able to identify it. As mentioned in the walkthrough example some PCs have an "ugly" power switch in the back, and a nicer one on the front. The nice button has no effect if the power is not turned on using the switch in the back first.
  3. Will the user recognize that the control will produce the desired effect?
    When the "Power" button is pressed but returns to its original position (it doesn't stay pushed in) the user may think it failed and press the button again, thereby turning the PC off again.
  4. After the action, will the user understand the feedback she gets (so she can go on to the next action)?
    Will the user check whether the green power light comes on after pressing the "Power" button? Will she realize that this light coming on means that the process of turning on the computer was successful?
A problem to watch out for is that the user may not be thinking what the designer expects her to think.
In the example we assumed that when the screen is dark the user will think the PC may not be powered on and go look for the green power light. However, if the user is more skilled, her first thought may be that the screen saver has kicked in, and that she should move the mouse or hit a key to "wake up" the PC.