First published this over here: Choosing a Hook | Piggie’s Place
It is really important that you choose the right hook for the yarn you are working with. First, you need to consider the project that you are making. How tight do you want your stitches to be? A smaller hook will make a smaller (tighter) stitch. But there are limits to what size of hook you can use with the yarn you have. Using a hook that is too small will lead to the yarn splitting while you work with it and that will make for uneven and ugly looking stitches.
I mostly make stuffed critters. When making these, it is important to have tight stitches so that the stuffing does not show through the finished fabric. Always select your yarn before you select your hook. When selecting a yarn, keep in mind that a fatter yarn will make a larger project.
Look at the pictures below as examples of how to select a hook.
The above is a G hook. The yarn fits completely into the hollow of the hook. I personally would consider this the largest hook to use. Going any bigger then this would create gaps in between the stitches, which is something to avoid when you’re stuffing the finished product.
The above hook is a F hook. The yarn just barely passes the tip of the hook. So, the yarn is just a little bit bigger then the hollow of the hook. This is a good match. You’ll get smaller stitches without having to fight with the yarn splitting.
The above hook is an E hook. The yarn is quite a bit bigger then the hollow of the hook. The tip of the hook falls about 1/2 the diameter of the yarn. I consider this the smallest hook I’d use for this yarn. Working with this hook will give you very small stitches which is great for stuffing. However, working with a hook this small risks splitting the yarn. If you use a hook this small, work slower then usual and re-work any stitches that split the yarn.