Apologies if this is a duplicate response...here are a couple that I find useful:
Q - at what point in a document's lifecycle should it be captured?
A - as close to the point of creation as possible.
Q - How do you define the technical requirements for an ECM solution?
A - Based on the business requirements, which requires an in-depth understanding of the WORK of the area that is getting ECM. Bonus points if they mention that ECM is supposed to automate the non-value added tasks, leaving the workers free to focus on the value-added tasks. More bonus points if they mention the system needs to conform to the existing IT infrastructure of the organization.
Q - How do you determine ROI for an ECM system? (this is a tough question because there is no "right" answer)
A - Anything that shows the candidate can apply logic to the situation, and that they understand it will be totally based on the application of the ECM solution. I'd give points to anyone that doesn't look like a deer in the headlights and you can eliminate anyone that says "it can't be done."

Hi Clare, Im going to assume some form of Consultancy so:

1. What does ECM mean to you?
Rationale: They will either give you a sales definition or if they understand it they will give you detail around the components, not just a technology etc

2. How do you scope an ECM implementation?
Rationale: ECM unlike DM or RM projects are much more programme based, usually new areas which the consultant wont be across, user interface, search optimisation, governance (more so in ECM), integration, ecosystem, records, capture

3. What is the most common mistake clients make in ECM projects
Rationale - for some reason people struggle to answer this, which usually indicates a lack of knowledge and experience. Clients mistake ECM (the vendor label) for ECM (the reality) this affects all stages of the project and from a consulting perspective, means the communciations, expectation setting, knowledge transfer, support etc all need to be increased significantly, not just from the Project Manager but by everyone involved.

Good luck.
Paula

Had to split my response :)

4. What is the biggest mistake you have personally made in an ECM project, what did you learn from it.
Rationale - everyone makes a mistake in their first ECM project, usually its not understanding the scale of it, what ECM means and what that means for reauirements gathering, project team roles etc. If they have never done one, you will see it immediately. A follow up may be to check whether this learning was an ECM project, or whether its another project and they are reusing :)

5. What roles would you see on an ECM project that you wouldnt see on an EDRMS, FMIS etc project.
Rationale - if they have done this before they will be able to tell you all of the roles, but focus on the common ones and the follow up then may be which ones do you think are critical and why.

And of course, Monica's questions below are also incredibly useful.

As ever though, you need to use the interview as one part of the assessment process, you may also want to get them to review a cae study, deliver a short presentation, and add additional questions as part of the referee checking process.

Happy to talk offline if you want to
Paula