Why 5? Why not 3? Why not 10?
Anyway, here's what you can do to improve user input (I am assuming when gathering the requirements and testing the system in software projects):
- Ask a lot of questions: Don't expect the user to tell you anything if you don't ask him. I have seen cases where there were monstrous bugs (in key features) that the users knew about but didn't say a word to the project manager because "he did not ask them".
- Study the business: You should know all the ins and out of the business before gathering the requirements. This way, you will ask the right questions and the user/client will answer the right answer.
- Be detailed: Again, if you don't ask, the users won't tell. Understand what every little feature that's in the system should do.
- Avoid assumptions when gathering the requirements: Don't assume that the user wants a certain feature to do a certain thing. Ask him.
- Be courteous and respectful: Treat users with respect and don't follow the bossy attitude. They will reward you by telling you what they want exactly, sometimes without you asking. Also don't forget, that uses can make your life horrible by "looking" for bugs or missing features if they don't like you, and by telling their managers that the software does nothing to improve their productivity.
(Reading my answer before submitting, I noticed that I assumed what you wanted, oh well...)