Short answer: A leading indicator is a data point that changes before the outcome reaches the headlines: marine insurance prices, the cost of insuring against a sovereign default, capital flows of sovereign wealth funds, government debt issuance, official visits and shifts in official language. A scenario starts to materialize when three indicators from different layers move in the same direction, not when one headline shouts.
The longer view
Money moves before words. Whoever insures ships, lends to governments or manages a sovereign fund pays for mistakes, so their behavior reveals what they actually think. Politicians' statements, by contrast, are a weak indicator, because they are aimed at a domestic audience. Rule of thumb: prefer indicators someone has paid money for.
For each scenario, set three to five indicators in advance, each with a numerical threshold. When the threshold is crossed, management executes the decision predefined for that scenario. The value of the method is not forecasting accuracy, but the fact that the decision is made in a moment of calm, not in a moment of panic.
This is a reading through the seven layers of The Blue Pumpkin, the method of Dr. Bella Barda-Bareket.
What to do tomorrow morning
For every scenario already defined, write down three indicators, a threshold for each, and the decision that will be made when the threshold is crossed.