hide the tail of the yarn. simply wrap the new yarn around the hook and draw up a loop and continue crocheting. leave a 6" long tail of yarn to, tie a loose knot to hold the yarn in place. when you complete your project, untie the knot and weave in the ends. this also applies when you have to change yarn in the middle of a row.
when a pattern says to change colors, it is made this way: work the last stitch to final two loops on the hook, draw up a loop with the new color and complete the stitch.
if you are following a color chart or crocheting 