Assuming you have the right person, the right topic, and the right approach, this step is about actually capturing their knowledge.   The key element in getting the job done is the characteristics and the skills of the Interviewer.  Here are some tips:

Characteristics of a good Interviewer

• Strong ability to listen, to draw someone out, to explore someone else’s experience and perceptions
• High tolerance for ambiguity and complexity
• Ability to move smoothly between specific cases and abstract rules
• Ability to put yourself in the shoes of the potential learner, to extrapolate what they would need
• Willing to learn new software

Audio editor, for cleaning up MP3 or WAV recordings of PowerPoint presentations or case studies
Microsoft Producer, for knitting together audio files and PowerPoint slides into a stand alone training file
Inspiration, for broad range of uses such as creating outlines (like this one) or graphic files. There is a tutorial available for how to use Inspiration, written in Inspiration.
WordPress blog system

• Comfortable with using audio visual equipment (recorders, video cameras, LCD projectors, etc.)

Key tasks

• Building a knowledge table, a map of the terrain
• Select the key topics to be covered

Material covered by existing manuals

Material best learned from outside training

Material that are good candidates for knowledge capture; more tacit knowledge; critical but not easily acquired through observation

• Decide on the appropriate strategy for knowledge capture
• Select a template for capturing the knowledge
• Generate a draft of the knowledge

Focus on the layer of the knowledge use that is consistent, repeatable
That is, the visible behavior may be highly variable, but the basis of the behavior may be a set line of questioning or analysis.

• Walk through the draft with the expert; test it against the cases considered

Does it capture the essence of the knowledge?
Does it define the missing pieces of the knowledge yet to be captured?

• Test the next version with a potential learner

Does it make the skill visible?
Can they imagine using the model?
Are they able to use it on a new case?

Explore cases of the knowledge use

• Listen for trends, commonalities, universals; look past unique or idiocyncratic details
• Listen for structure of the underlying database(s) involved

Simple lists
Formal database (cases, fields, relational links)
Node-link structure

• Listen for the steps, process flow, sequence of work
• Listen for the degree of consistency or repeatability

Source: Jerry Talley