This Boye yarn threader is a tool I just can't live without! These little yarn threaders make quick work of a tiresome job of weaving in ends. You simply push the hook of the threader through the eye of your yarn needle, grasp the yarn and pull it back through the needle. Now you're ready to roll!
What I love about this particular brand is that they are sturdy and strong. There are two hook sizes, one on each end, for threading different size yarns.The smaller end works great for crochet threads. I use the larger hook end for medium weight and larger size yarns. You can see in the photo below that you can also easily pull through two ends of yarn at the same time. You just have to use the correct yarn needle size to accommodate your yarn thickness.
There are other types of yarn threaders out there, particullarly ones with thin wire ends. I don't like those threaders because it doesn't take long for the wire to break, and to me, the whole point is not having to try and jab the yarn through the needle, and with the wire ends you are still jabbing the yarn through the needle threader.
I have several of these and keep them in my crochet kits so they are always at hand. If you've never used this type of threader, give them a try, you'll be pleasantly surprised at their usefulness!