Knitting in the round, using either circular or double pointed needles, creates a seamless tube of knitting, ideal for making socks, hats, mittens and sweaters. One of several advantages to knitting in the round is that the right side of the work is always facing youso with Stocking Stitch for example, you would knit every row. Charted patterns will be read from right to left for every row and all stitches will be knit as for the right side. What could be easier? Another benefit - there's very little finishing work to do since there are few, if any, seams to be sewn when your items are made "in the round".
Use circular needles for larger diameter circular knitting, like sweaters. The stitches should fit easily along the needle without stretching, so use a needle with a length that is slightly shorter than the circumference of the item you're knitting. For example, you'll need a 16 inch long needle if you're making a hat with a finished circumference of 18 inches.
To begin, cast your stitches onto one end of the needle just as you would with a straight needle, and place a stitch marker on the needle to mark the end of the row. You'll start by first making sure that your cast on stitches are straight on the needle and not twisted (twisting cannot be corrected later), then knitting into the first cast on stitch you made, from the other end of the needle. This connects both ends together and you should end up with a circle of stitches that will be the foundation for your project. Work the first round, following your pattern instructions, and when you come back to the marker you'll have completed one round. Watch this video to learn more about getting started with circular needles.
Knitting in the Round Using Double Pointed Needles
Most double pointed needle sets in North America contain 4 needles - three for holding the stitches and one for knitting with. Sometimes you can find them containing 5 needles which many knitters prefer for working in the round, as it creates a little less pull on the loop between each needle. Whichever set you use, put one needle aside and divide your stitches evenly between the remaining needles.
Now join the needles into a triangle, if using a set of four or a square, if using a set of five, making sure your cast on stitches aren't twisted. They should all be facing toward the inside of your triangle or square. Place a stitch marker on your needle and, using the one that you'd set aside, begin a round by knitting the first cast on stitch as the first stitch of the round. Once you've worked all the stitches from the first needle, it now becomes your free needle for working the stitches from needle #2. Needle #2 then becomes your free needle, and so on. Watch this video to learn more about getting started using double pointed needles.
It'll take some practice to get comfortable using all those needles but just remember that you're only ever holding two needles at a time - the one with the stitches to be knit next and the one to knit them with. The others are hanging free until you get to them. The thought of using these needles can intimidate novice knitters but with a bit of practice you'll have it mastered and you might even find that you prefer knitting in the round, like so many others do.
To begin, cast your stitches onto one end of the needle just as you would with a straight needle, and place a stitch marker on the needle to mark the end of the row. You'll start by first making sure that your cast on stitches are straight on the needle and not twisted (twisting cannot be corrected later), then knitting into the first cast on stitch you made, from the other end of the needle. This connects both ends together and you should end up with a circle of stitches that will be the foundation for your project. Work the first round, following your pattern instructions, and when you come back to the marker you'll have completed one round. .jpg)
Now join the needles into a triangle, if using a set of four or a square, if using a set of five, making sure your cast on stitches aren't twisted. They should all be facing toward the inside of your triangle or square. Place a stitch marker on your needle and, using the one that you'd set aside, begin a round by knitting the first cast on stitch as the first stitch of the round. Once you've worked all the stitches from the first needle, it now becomes your free needle for working the stitches from needle #2. Needle #2 then becomes your free needle, and so on. 
