Nonfunctional requirements describe aspects of the system that do not map onto a single piece of functionality. Essentially, they're constraints you need to operate within. Allan Kelly details how running performance tests regularly can be the key to nonfunctional requirements, as well as how much value these constraints produce.

Acceptance criteria can be helpful in expanding on user stories in order to capture requirements for agile projects. However, acceptance criteria should not be a route back to long, detailed documents, and they are not a substitute for a conversation. This article tells you how and when acceptance criteria should be written and employed.

Some teams only work with stories, but it can be difficult for a team new to agile to write stories that are easy to understand and provide value every time. An alternative is to add epics and tasks. Understanding the differences between each level and knowing what size story to use for each situation will improve the accuracy of your sprint planning.

Agile emphasizes just-in-time requirements rather than upfront preparation. The requirements person—be it the product owner, business analyst, product manager, or someone else—embodies the understanding of what is needed, and the user story represents the work that needs doing. This article details what user stories are (and what they are not).