I'm not sure who gave me this tip, but as a hat maker let me just say that it was one of the BEST tips I ever received! If you make a lot of hats, or anything that's worked in the round, you NEED to know how to start with the Magic Ring! It's also sometimes called the Magic Loop (not to be confused with the magic loop used in knitting) or Adjustable Ring or Sliding Loop. Whatever you want to call it... LEARN IT! I've seen some hats in people's shops where they're still using the Ch-4/join method. No no no... that little hole in the top of the hat looks icky!
When you use the magic ring, you can pull the tail thread and the circle can be cinched totally closed. No more holes!
<-- See a hole? Nope. That's how it should be. :)
On crochetme.com, there is a step-by-step tutorial with photos... this is the page I used to learn the magic ring. It was SO helpful! CLICK HERE
There are also various videos on YouTube that you can watch to learn the method. Sometimes watching them over and over is helpful. Just search for "magic ring crochet" or CLICK HERE for a good one.
Hope you found these links to be helpful! Happy Crocheting!