What's "Hook-Led Gauge"? Why is it Important?

Learning how to let your crochet hook determine your stitch gauge is possibly the most valuable skill a crocheter could develop. 

Why?

• It breaks a common habit that crocheters traditionally fall into: making their chains and slip stitches tighter than their other stitches, regardless of their hook size. Sometimes the crocheter simply crochets much more tightly or loosely no matter what size hook they're using. Other crocheters are actually using the yarn as a gauge guide. Crocheters who are used to using a lot of cotton yarn or thread, which is not stretchy to work with, tend to do this. 
•  It's necessary for making fashionable-looking crochet fabrics with dramatic drape and textures. Sometimes I think of it as "crocheting with air" -- that's how it might feel to use a very big crochet hook with a fine or very stretchy yarn.
• It comes in handy when making Love Knots and other intermediate-level stitches that depend on being able to "eyeball" a loop size.
• You'll be ahead of the curve if you'd like to someday crochet professionally as a Teacher, Designer or as a valuable Pattern Tester for other Designers! 

Every crocheter starts out with a natural gauge, often called the "crocheter's hand." With enough practice, crocheters can have more control over their natural stitch gauge. This is actually an intermediate skill that leads to advanced crocheting, although it's not listed in any of the standard skill level descriptions.

To maintain the best stitch gauge throughout, use the diameter of your hook to judge if your stitches are the right size: as you crochet, the space between the two top loops of each stitch should look large enough to fit the size of the crochet hook you're using. 

You might feel a bit outside of your comfort zone at first. If so, just tell yourself that you're making an important investment in your hobby: a world of exciting new stitches and designs will open up to you.