In the realm of social ritual and celebration, the bachelor party has held a position of prominence for time immemorial. A rite of passage, a final hurrah, or a celebration of impending conjugal bliss – regardless of the lexicon employed, the essence remains the same. This seminal event, therefore, requires meticulous planning, often entrusted to the capable hands of a Bachelor Party Planner. However, this selection must not be made in haste. It is critical to pose the right questions to ensure an event that matches the vision, personality, and preferences of the bachelor.

The selection of a party planner can be equated to an exercise in statistical decision theory, wherein you aim to minimize the risk or cost associated with a 'wrong' decision. Hence, the first question should be aimed at understanding the planner's level of experience and their expertise in curating events similar to your vision. This would include their understanding and navigation of the local party scene, their connections and network, and their ability to improvise and problem-solve.

Ask them to share examples of previous events managed, client testimonials, and any unique scenarios they may have encountered and overcome. In tandem, delve into their understanding of your specific requirements. Bachelor parties can range from the quintessential bacchanalia to a serene retreat into nature, or a culinary exploration. A planner with a diverse portfolio would be more adept at tailoring an event to your specific needs.

The second question should concern logistics and planning. An understanding of project management is pivotal here. A good planner should demonstrate their proficiency in time management, resource allocation, and risk management. They could adopt either a Waterfall or Agile approach to planning, and their choice would depend on the complexity and duration of the event.

The Waterfall method, with its linear, sequential approach, would be suitable for a straightforward, one-day event. On the other hand, an Agile approach, with its iterative and incremental practices, would be more suitable for a complex, multi-day event. It is essential that the planner can adapt their methodology based on the requirements of your party.

Next, inquire about their cost structure and financial management. It is well established in economic theory that individuals have different risk preferences. Some may be risk-averse, preferring a fixed cost contract, while others may be more risk-tolerant, opting for a cost-plus contract. The planner should be able to discuss the benefits and drawbacks of each approach and suggest the best option given your budget and risk preference.

Further, invoke the theory of comparative advantage, a fundamental concept in economics. Rather than attempting to manage all aspects of the event themselves, the planner should be able to delegate tasks to vendors who specialize in those areas, thereby ensuring optimal efficiency and quality.

Lastly, consider their communication style and crisis management strategies. Communication is the bedrock of any successful event. Ensure the planner is clear, concise, and accessible. In addition, understand their approach towards potential crises. Here, the Pareto principle comes into play, which posits that 80 percent of consequences stem from 20 percent of causes. The planner should be adept at identifying and mitigating these high-impact risks.

In conclusion, selecting the right bachelor party planner is not a decision to be made lightly. It requires a deep understanding of various theories and principles, from statistical decision theory to project management methodologies, economic theories, and risk principles. By asking these critical questions, you can ensure an unforgettable bachelor party that truly celebrates the uniqueness of the guest of honor.