I've chosen a very simple hat pattern for my first attempt at knitting with two colours. I'm just unsure whether I should carry the yarn up, or cut it after each row. It's only a small amount of each colour - yarn A - knit one row, purl one row. Yarn B - knit one row, purl one row etc etc. I'm thinking I should cut it after each row? But I'd much rather have an expert opinion!!