What is the initial step that an information security manager would take during the requirements gathering phase of an IT project to avoid project failure?

Ensure that the business problem is clearly understood before working on the solution.

Explanation:

To avoid project failure, the initial step in the requirement gathering phase of an IT project is the basic understanding of the real and actual motivation that is behind what is required.

A good and concise understanding of the problem is needed first before a solution can be offered to this problem. If the business problem is unknown or not understood then the project would likely end up as a failure because the solution offered may not be the right one.