Here are some tips for glazing:
Become familiar with transparent colors. Run tests on your tubes of paint so you can see for yourself which colors will be transparent, semi-transparent, or opaque. Some manufacturers will put this on their tubes but it always best to find out how the paint works for you. And never assume that a given color from one manufacturer will work the same as that given color from a different manufacturer.
Keep opaque colors for the bottom layers that will be glazed over.
Be extremely patient. If you apply a glaze over paint that isn't totally dry the layers of paint will mix together. The paint must be dry to the touch. Work on several paintings at the same time so you can move from one to another while they are drying.
Understand the ground color: Try using a dark ground and a light one. Lighter color will reflect the color much as with watercolor. Darker color will absorb light. If you experiment with both you will discover what effect you want to show in your paintings.
When thinning acrylic, the only 'rule' is to not mix paint with more than 50 per cent water. You may want to use a medium to thin the paint. If so, you can mix in as much medium as you like because it's got the acrylic resin in it that makes the paint stick to the support. As with most art medium, things will work best if you use artist's quality.
Using a soft, rounded brush will work better than a stiff, hogs-hair brush in applying glazes without brush marks.
Unify a painting with a final glaze. When your painting is finished, apply one final glaze over the whole painting. This helps unify all the parts of the painting. Or you may apply a final unifying glaze to just the elements in the focal point. Experiment with final glazes to get the effect you like best.