Initial Requirements

From the information collected by your user surveys, both formal (questionnaires) and informal (chatting and observation), you should be able to write down a description of what the eventual system will provide. In any interactive system, these requirements are likely to change: new technologies develop, new ideas appear, and new tasks become apparent, often only after there is some form of initial system that can be used. The initial requirements should not therefore be seen as a fixed goal; they are more a milestone towards a final, user-centred system.

Reading

Chapter 5 - The Design Process, pp. 147-189

Some advice

You should concentrate on analysing the task at hand from the viewpoint of the users. There are a number of factors that have to be considered in the design, ranging from the way information is entered into the system and the manner in which is presented back to the user, through aesthetic judgements and down to the functionality that the system should offer. Some of this is relevant to determining the requirements, whilst other aspects come more to the fore when you actually get down to doing the design.

Unfortunately for you, the view of your prospective users is more important than yours, and so your task as a good designer is to find out what it is that they require and produce a system that meets their needs.

Consider the user responses you have collected, and then analyse them under the following headings:

Functionality
You are looking to determine what particular tasks the users wishes to accomplish , and how they want to go about those tasks. You are trying to decide what features you should offer and what you should miss out. You are (somewhat) constrained by real-life costs and certainly by time, so will have to make certain trade offs.
Try to decide what the real issues are that people will consider when using your system. Try to see what factors will influence their decision about whether or not to use your system. It is these that must motivate your design. Make a list of the features that you feel your system must have.
Interface
How are you going to present all this information to the user? What manner of output would be most suitable? What is the best way to interact with this output e.g. hotspots, or menus, or text, or something different? Will you present all the information at once? What input characteristics will your system have: how will information be entered, functions accessed, and so on?
Aesthetics
Consider issues of overall colour, size, shape, texture, of button spacing, layout, colour and feedback, display size and placement, information display etc.
Remember that the intention is to produce a device that offers optimal performance for the large majority of users.
Make full notes of your views, with supporting evidence. This forms the user requirements specification, which is to be handed in for assessment. This will be used to drive the design of the system, and you must be able to back up the design decisions that you have made ("well, I know that the system is pink and blue, but 16 out of 17 people wanted this colour scheme at the expense of legibility....." is better that "it seemed like a good idea at the time").