Be structured, build an answer tree:
1. Ask for time (though BCG at least will probably never accomodate, "the client is in front of you and asks for an update)
2. Top of the tree, level set and remind me what the question was
3. Answer first. "I have 3 recommendations: A, B & C". I call this the "go horizontal" phase, as you will simply count and list the recommendations, no explanation yet.
4. Come back to each recommendation and detail them. I call this the "go vertical" phase, as you now really drill down into each recommendation: what you found, how that is relevant, what it will give you; make sure to point out if a recommendation is 90% of the answer, or if one must be implemented before the next btw.
5. Next steps: Either (5a) something else you haven't had time to implement yet, or (5b) offer to help implement the current recommendations. I also put risks in there, if needed: "we understand changing the comp structure of your sales force can be a little daunting; rest assured, we have experience doing this and would love to help you implement this recommendation"