YOU HAVE TO FEEL THE SOIL
This is the AAA, the First and Foremost, the Most Especially Important Secret of the Green Thumb!
If you've never been able to quite understand the variations between "wet" and "dry", or if you're not sure that what you mean by "moist" is the same as what someone else means, here's a little thing you can do at home. Take a small handful - a couple of tablespoons - of potting soil or potting medium, and make sure it is completely dry; you may have to microwave it awhile, or let it sit around for a few days. Then put it into a small bowl, and pinch some between your fingers. This is "dry," this is what people mean if they use the term "completely dry." Now start adding water a little at a time - about 1/4 teaspoon - and stir it around well. Let it sit for a few minutes after each addition of water, to allow the particles in the soil to absorb the water. Pick up a little soil and squeeze it after each portion of water has been absorbed , try to feel how it changes from the barest hint of moisture to soft and cool to dripping wet. Match your samples to the moisture chart to check what you should be looking for.