Knitting with two different size needles makes a project go fast if one of the needles is a Size 15, and the smaller is a Size 6. The larger needle's bigger stitches create a lacy effect without doing any yarn over stitches and decreases. You don't need two sets of needles if you own a set of interchangeable circular needles because a larger size needle can go on one side of the cable and a smaller one can go on the other side.
Cast on 30 stitches on the smaller knitting needle.
Knit one row with the Size 6 needles. To knit, hold the needle with the cast-on stitches in the left hand. Hold the empty needle in the right hand. Take hold of the working yarn with the right hand, and hold it behind the right needle. Insert the empty needle from front to back through the first stitch on the left needle. The right needle is underneath the left needle. Bring the right hand and forefinger toward the tip of the right needle with the yarn underneath the right needle. Wrap the yarn around the right needle from back to front. Be careful not to wrap it around the left needle, too. Keep the yarn firmly tensioned in your right hand and bring the right needle toward the yarn, pulling a new loop through the old stitch. Slip the old stitch off the left needle.
Knit one row with the Size 15 needle.
Repeat Rows 1 and 2 until the scarf is the desired length. Bind off all stitches with the smaller needles. To bind off, knit two stitches, lift the first stitch worked up and over the second stitch and off of the needle. Repeat to the end. Pull the yarn through the final loop.