You can buy a special long hook for large projects, but if you're doing something narrow like a scarf (or a granny square) you can use a standard crochet hook!
I'm using the cursed Premier sock weight yarn (the yarn isn't really cursed, just the socks were) and an E hook (the top of the recommended range) - it's a good idea to go up in hook size to avoid tension issues and curling. I still have curling, but I think it will block out.
I'm showing you the diagonal stitch (new to me) in a variegated yarn; if you want to see more options for working this stitch, I recommend visiting Stitch Diva - she has very good tutorials on how to execute the basic stitches (flat and in-the-round), as well as a series of classes you can purchase from her (not an affiliate post, I just really appreciate stitchers who put effort into teaching others!) - she also has free and paid patterns available. (Here's one of the free ones - chainmaille! It uses this stitch!)
On to the project!
The diagonal stitch reminds me of Entrelac knitting. Especially when I did a block of about 11 stitches, 11 rows high (I don't know why 11, it's just the number I picked). I saw the left-hand edge looked an awful lot like slipped stitches that would be easy to pick up to start another block, so I did, and made a cool tulip-v-shaped thing:
Then I wondered what would happen if I picked up stitches on the right-hand edge of piece #2, and slipped each row to the top of piece #1 as I worked. This happens:
It's like a hexagonal granny! (I think it was pretty easy to figure out as I looked at it, but if you want a step-by-step for creating this granny, let me know in the comments!)
I think I've found some 12-y Seahawk redemption for this yarn, and I may try making my first real afghan out of these! I started a grey one, too - I just need to get some off-white sock yarn to edge and attach the pieces!
You could also assemble them more like a puzzle, making 2 of the v-shaped-tulips and turning them points in. There are a lot of really neat options with this idea. What would you do with this stitch?