A simple jury stick is a great tool for judging when several cups of simmering liquid has reduced to just a few cups of simmering liquid - when we have enough forethought to actually make one. But when I'm just reducing a quick pan sauce by half, I've found that just tilting the pan is much easier.When a sauce is spread out over the bottom of a shallow pan, it's hard to really judge if I have a whole cup or just a few tablespoons. Tilting the pan pools all the liquid to one area and makes it much easier to estimate the amount. If I remember to tilt the pan to check the amount when I start reducing a sauce, this also makes it easy to tell when the sauce has reduced by half.
The more often I do this, the more accurate I find that I become. Do you use this trick, too?