Before I guide us through casting on, I just want to talk a little bit more about the yarns, just in case you're still undecided.
I mentioned before that I used sock yarn scraps for my #wwscrapalong Hats, and amongst those scraps were some mini skeins that I came home with from TNNA. Mini skeins are absolutely perfect for this project, as you can mix and match them with your leftovers and oddments for variety and colour. Gradients are also perfect, as are your handspun leftovers or other small lengths of precious yarn.
But you don't have to use sock weight or 4ply!
I have worked out the numbers for weights up to chunky, so you have plenty to choose from. If the most common weight in your stash is worsted, so be it - knit it in worsted!
You can also mix up yarn weights, too! If your main yarn weight is say, DK, you can still knit a stripe or three in 4ply or even lace weight - it will appear lacey and drape beautifully.
Or you can mix yarns together, holding two or three strands of laceweight, or two strands of 4ply - don't be afraid to experiment! The beauty of working with small amounts of yarn each time is that if you don't like how a stripe has worked up, you can rip out that stripe - it's just a few rows.
Once you've sorted out your yarns, you're ready to cast on!