Knitting carrying yarn up - catching it behind the stitch. I'm using this technique to alternate hand-dyed yarns for a lace shawl. It's amazing, because the loops on the side are pretty much invisible!
Cocoknits Tutorial: No More Estimating Tail Length for a Long Tail CO // Use this technique to avoid estimating for a long tail cast on. You'll get the neat edge of the long-tail method without the fuss.