In my crochet classes we are working on a scarf pattern by Lion Brand Yarn. The pattern says it only requires "one ball" to complete the scarf. However, one of my students ran out of yarn half way through.

Lesson: Be sure to check the pattern for the amount of yarn required. The yarn my student was using comes in skeins of 3.5 oz (147 yrds). The yarn the pattern suggests comes in skeins  5.3 oz (312 yrds). This is something you will want to remember when selecting yarn for your projects.