It all begins and ends with yarn. Choose wisely! Whether you have found a pattern that trips your trigger and are seeking the perfect yarn for it, or whether you’ve got the yarn and are looking for the perfect pattern, the success of your project will depend on how well you paired the yarn to the design. Even if you are using the same yarn called for in the pattern, it is important to swatch, not only to determine if you need to make adjustments to needle sizes, but you might find out that there is  quality to the yarn that poses a challenge you don’t want to take on. Some yarn features to consider: Fiber content, weight, WPI/ sts per inch, color. A huge topic of debate among knitting groups is whether cost should be a consideration, or amount of yarn already in one’s stash.
Yarn Substitutions
A Tutorial for Substituting Yarn in Any Pattern by Nordicmart
Ellen Susanne Designs 