I like to use this technique to join new yarn for amigurumi and any other project I am working in single crochet.
How To Join New Yarn with a Single Crochet Stitch
Step A: Place a slipknot on your crochet hook.
Step B: Insert your hook into the specified stitch.
Step C: Yarn over the hook and pull one loop through the stitch (2-loops on the hook).
Step D: Yarn over the hook and pull through both loops. You have completed the first single crochet of the row.
Step E: Continue with the pattern instructions. The photo shows the joining stitch and 5-additional single crochet stitches.
Super simple right? and you can’t tell it is a joining stitch.
When I use this type of joining method, I swing the tail of the yarn behind the work and crochet over it as I go – so I don’t have any yarn ends to sew in afterwards.