Kim Werker, former editor of Interweave Crochet and co-host of Knitting Daily TV, demonstrates how to change yarn in the middle of your work.
When do you tie it off or cut it off. I'm new at crocheting.
Lydia, as soon as you have joined the new color and have crocheted a couple of stitches, you can cut the old, leaving a long enough tail to weave it in later. If you plan to pick up the first color again, do not cut it off, but just let it hang until you get back to it.
Hope that is clear. If not, perhaps someone else can explain it better.