There is no hard and fast rule. cut and paste go together, and are very useful, along with join. cat is not needed that much. grep finds lines. sed makes quick arbitrary changes. awk works well with fields and can make programs. bash ties it all together, and can make programs. The main thing I would recommend is keep the code easy to read and maintain, even for other viewers. Emphasize readability over performance. Avoid trying to always do everything with awk, or always do everything with perl. It sounds like you already know it's better to learn a variety of commands, such as the key ones you mentioned, and a few others such as uniq, head, tail, and sort, and use the commands within the context of shell scripts.