Three ways I can think of: cms, Snellen, and your vision outside.
For cms: download Varakari’s Vision Log Tool. Get a tape measure and measure your distance from the screen to where there is no blur at all, and enter the cms into the tool. It will tell you your diopters - you should end up with a nice chart over time that shows improvement in the long term.
For Snellen: hang up a 3m or 6m Snellen chart in your home and guage how well you can see it with your current pair of normalised. See the acuity of the text, whether it’s blurrry etc. In one, two, three+ weeks there should be an improvement if you’re doing all the other stuff correctly.
I find that it is easier to Active Focus when I have made improvement relative to the reduced normalised glasses I’m currently wearing. You’ll walk past the same sign, with the same pair of normalised, same distance and you’ll see that it is easier to see now than it was two weeks ago. This is really motivating.
Measurement is important when starting out to see if you’re getting things right or wrong, highly recommended. You will over time learn to use your results from measurement to judge whether you should make a reduction in your normalised diopters or not. This is like walking a tightrope, it’s very easy to reduce too quickly, but you can also reduce too slowly at the same time and miss out on potential gains.