It's a well-known advice that: When usability testing, start with the easiest task so the participant can get the hang of thinking aloud and gain some confidence. This will increase data quality.
In my experience, however, there is a logical order to tasks. I can't just rip one out and put it to the front. So what to do then?
One easy task that we can always give participants is an exploration task: "Look around and tell me what you make of it". Be mindful though, this is not a good usability test task, because exploration is not realistic use. Discard its results.
So an exploration task is good for
- boosting the participant's confidence,
- practicing think-aloud.
And it can be also used to
- establish a baseline familiarity with the product.
For example when I test b2b software features it can be very challenging for a participant to land on a completely unfamiliar product, and start to use one of its features. At that point, the participant doesn't understand the context of that feature, let alone the higher-level logic of the product. This is where a little exploration can help. Ask them to look around, get a general sense of what the product does, how it works, and only then start the test with the feature of interest.