When it comes to designing any sort of product, whether it be a web page, an appliance, etc., the needs of the end users should be taken into consideration every step of the way. That way, we as Human Factors researchers can design and test a product that has the best chance of success.
User needs analysis is a critical step in the process of prototyping a product. It is the process through which researchers differentiate the most likely users from the rest of the population, generally using aspects such as technology expertise, task expertise, age. Just about any characteristic that affects how one interacts with the problem would be relevant. For example, if we were to design a patient portal for use in a doctor's office, the patient-facing pages would look very different from the practitioner-facing pages. This is because these two groups have a fundamental difference in knowledge when it comes to medical terminology.
As such, before we start designing the product, we must talk to the users! Sometimes also referred to as "subject matter experts" (SME) depending on the context, they are your best bet to having a strong start to designing the actual product. This can be done via methods such as surveys, focus groups, tasks analyses, there is a wide variety that one can use.
Since usability is at the heart of Human Factors, let us look at an example from an ongoing study by Celia Henderson. Her research is currently centered on accessibility technology/devices and how to improve them. Her current study specifically looks at text-to-speech(TTS)/AI voices and how best to manipulate them to better convey structural aspects of the text (e.g. headers and italicized information).
In this case, a focus group was utilized. A focus group is when a researcher leads a guided discussion using a list of pre-determined questions with a group of people from the target population. Another important feature of this method is that although we use a pre-determined list, we will ask followup questions based on the responses of the participant.
In this particular case, the target audience was visually impaired users of accessibility technology such as screen readers. The questions were all related to their use and interaction with existing TTS technology (e.g. "what are some barriers to you using this technology"). Their responses largely centered on the TTS voice's inability to convey things like headers or bolded text, which prompted further questions. Those questions then led to a study to test manipulations to the voice to improve user experience with TTS technology.
Dillon, A., & Watson, C. (1996). User analysis in HCI - the historical lessons from individual differences research. International Journal of Human-Computer Studies, 45, 619–637.
Lindgaard, G., Dillon, R., Tvbovich, P., White, R., Fernandes, G., Lundahl, S., & Pinnamaneni, A. (2006). User Needs Analysis and requirements engineering: Theory and practice. Interacting With Computers, 18(1), 47–70.