If you want a practical tip, I suggest using a digital caliper for this. Before you start, just double-check that your firearm is unloaded and safe to handle. Keep the slide forward and press down the trigger all the way, then measure the distance from the back of the trigger shoe to a stable point on the frame. Usually, the inside of the trigger guard works perfectly for this. Once you got the measurement, gently let the trigger go until you hear that reset click, and measure that distance again from the same 2pts. The difference between those 2 numbers is your reset length. I love this method because it gives you a clear number to track, especially if you're tinkering with new parts or trying out different guns. For best results, I recommend doing this a few times and averaging the measurements. If you’re really keen on nailing down your trigger feel, this way lets you see the changes and make smarter adjustments.
