Crochet until you run out of yarn. Stopping at the end of a row is best, if
possible, but you can also change colors in the middle of a row.
If you are changing colors at the end of a row, turn your work around, like you would to start a new row. Trim your yarn off. (about 2-3 inches)
Insert you hook through your next space. Grab your new color of yarn and pull it through.
Chain 1. In these pictures, I am using a single stitch, but it doesn't matter what stitch you are using. Make your stitch in the same space.
Crochet over your yarn tails, and then weave them in. Continue your project.
Changing in knitting is basically the same. Just grab your new color of yarn, and start working with it.
Hope this helps, Kate!