Circular knitting needles are a wonderful alternative to knitting with multiple double pointed needles. However, the way the needles are stored and packaged, can make for a curled up mess. Generally, the flexible part of the circular knitting needles will need to be relaxed and straightened before you can use them effectively.
The most effective way to straighten your brand new circular knitting needles is to apply some form of heat to the flexible cord connecting the actual needles. A word of caution however: if you are straightening bamboo circular knitting needles, just make sure that you do not damage the bamboo by applying heat to the wood.
Probably the easiest, most foolproof method of straightening out the curling is to use hot, almost boiling water. Add water to a saucepan and heat the water until it is almost boiling. You will want to have an area big enough to stretch out your circular knitting needles once you have dipped the flexible connector into the very hot water for less than a minute. Leaving the cord in the hot water for any longer may not harm it, but it is better to not take chances. After applying the heat, stretch the circular knitting needles out on a towel.
At this point, you can either keep the needles stretched out using your hands, or you could lay something heavy on top of them and just leave them until they cool off. Fold the towel over the top of the needles and lay a skillet or brick on top. Hopefully this method will work the first time you do it, but occasionally circular knitting needles are stubborn and require more than one application of heat to fix the problem.
Another easy way to apply heat is to use an iron. This is a more delicate operation, and needs to be done with a lot of care so that the circular knitting needles are not ruined. This method requires a bath towel and a clothes iron. Heat your iron to the lowest setting. Fold the towel over the stretched out circular knitting needles and apply heat from the iron through the towel until they are straightened out.
The basic method for both of these processes is the same; applying heat to the plastic, which, in turn, will allow the needle connector to relax and straighten out.