I’ve been doing some remote automated usability testing of late. I have to say asking those questions is very difficult indeed! I generally use the same principles as for face to face.

You need to make sure people are clear on what you want them to do without giving it away.

Then you need to make sure the follow up questions don’t put words in the participants virtual mouths.

Another struggle is not asking too many questions, and maintaining the participants attention!

The overall difficulty is how you get them to provide useful feedback when you are not sitting next to them to understand why they have done certain things.

As with any testing you always need to triangulate on method with another. That said the power of quantitative data to get the clients attention is awesome!