Cut the wool yarn end cleanly
Hold the new yarn tail alongside the old yarn tail
Place the new yarn where you want to join it
Make a slip knot with the new yarn if needed
Insert the hook into the next stitch
Yarn over with both strands if joining in the middle of a row
Pull the new yarn through the stitch
Continue crocheting with the new yarn
Leave short tails for weaving in later
Weave in the ends securely with a yarn needle
Check that the join is tight and even