Planning Grilled veggies stacked with goat cheese and a balsamic reduction fir a vegetarian friend but need tips for how to do the reduction

Boil lightly to reduce by half. Don't be alarmed if it seems too liquids - it will thicken as it cools.
If not thick enough, boil then cool a bit more.
If using a cheaper balsamic, you might want to add a pinch of sugar.