If you want to be a bad product manager, dictate solutions. You’re the product manager, after all, and you know what’s best for the product. How are other people going to know what to create if you don’t tell them what the solution should be? If you don’t tell them explicitly, then they’ll probably end up creating something that’s not even close to what you were asking for. And when you tell others that the search results page has to use AJAX or that the possible choices for registration should be listed in a dropdown box, don’t waste time explaining why you want those solutions. It’s your job to know why, it’s their job to build it.
If you want to be a good product manager, clearly articulate market problems and needs and the associated requirements. As a product manager, your job is not to come up with solutions — there are plenty of others who are devoted to that. Your responsibility is to understand the market, identify customer needs, and describe the aspects of the product that will solve those needs. Any solution that fills those needs should suffice, and it’s the responsiblity of others on the product development team to come up with the best solutions that meet those needs.
If that makes you feel a bit uncomfortable — not controlling all aspects of the product — ask yourself why. Is there a particular idea that you’re completely wedded to for some reason? Are you afraid that there are requirements that you haven’t communicated, increasing the likelihood that a solution will be designed that won’t meet some of your requirements? Do you not trust others to come up with different or innovative ways of approaching the problem? Do you not trust others to come up with a solution at all? Often product managers feel the need to dictate solutions not because they are naive and think it’s something they should do but due to some other underlying issues.
Ultimately, product managers are most successful when they can communicate not just the requirements for what the product needs to do but why the product needs to do that. That detail helps others understand the drivers behind the requirements but leaves enough latitude for innovative new solutions to be created that can meet the requirements and solve the underlying customer needs.