The aim of this exercise is to help the members of the group to identify symbolic gestures, actions, or pithy sayings that they have seen or heard - perhaps, indeed probably, in a very secular context, and then to reflect on what they might tell about God. By extension, the hope is that members' awareness of God speaking in this way will be heightened, and they will be more open in the future.
It will probably be helpful to introduce the exercise with an example. You might go to the Bible and do a simple and brief study on the story of Jesus washing His disciples' feet (John 13) - an ordinary, everyday courtesy, which nevertheless carried a powerful truth. You could invite the group to reflect on why it was necessary for people to have their feet washed? Are there other examples of this custom in the Bible? Who would normally do the washing of others' feet? What precisely would be physically involved? What point was Jesus seeking to make by doing this? How do you think the disciples felt?
If you had water, bowls, and towels available, you might feel it appropriate to invite the group to wash each others' feet and then reflect on the experience. Not all groups will feel comfortable with this and there might be practical problems in removing the necessary footwear so think carefully before suggesting it.
You could then invite people, perhaps in twos, to identify other ordinary everyday actions which might speak of God and to share these insights.
The group might finally be invited to look out for other examples to be shared at the next meeting.