Before suggesting ideas that I believe can change things, I’ll post some things I think won’t change much in the long term.
I pointed out what appears the dominant strategy for North Korean decision-makers

1. Stabiility: to maintain its geographical dominance
2. Loyalty: to maintain its support from its citizens

All other decisions are subordinate to this strategy or irrelevant. I expect the North Korean government will resist any action that threatens those two principles. And I expect only actions that affect those points will make much difference (though many small actions in other areas may collectively make a big difference).
I also pointed out the stakes to individual North Korean decision-makers. They care about the situation more than you do. Any strategy that leads North Korean decision-makers to feel their system is threatened will likely make them feel they, their families, and everyone they know is in grave danger. Backed into a corner, the option to fire missiles on Seoul or Japan becomes more palatable to them — they may feel they are fighting for their lives as well as those of their families and everyone they know.
They can also influence things more in North Korea. The combination of greater power and motivation suggests competing against them will be difficult.
History has borne out the above. Since the end of the Korean War

• No military action has changed North Korean policy. The risk of retaliation on South Korea and Japan are too great. With nuclear weapons, the risks to the United States become too great too.
• No economic aid changed North Korean policy. North Korean decision-makers resisted aid offered with conditions that would have conflicted with their strategy.
• No sanctions changed North Korean policy. They don’t affect the strategy above.
• Diplomacy hasn’t changed North Korean policy. Again, proposed changes that don’t affect the above don’t change anything. They resist changes that do.
• Cutting off diplomatic relations won’t change things either, by the same token.
• North Korean people can’t affect the core strategy individually and draconian punishments prevent large enough groups from forming.
• Famine contributing to the deaths of roughly ten percent of the population didn’t affect North Korean strategy. As long as some part of the population can produce enough to supply enough resources to sustain the decision-makers’ standards of living, they will maintain their policy.
• Publicizing the situation there to the outside world hasn’t changed things. People outside North Korea can’t affect the above strategy (though little things in this area could add up, especially if they affected China).

Based on history and the strategy above, I don’t think the following would change much in North Korean policy, though I don’t think the non-military ones would hurt either.

• Military action
• Economic aid
• Economic sanctions
• Diplomacy
• Cutting off diplomatic relations
• Publicizing the situation there to the outside world

On the other hand, I don’t see visiting North Korea as tourists affecting the situation either. In fact, if tourism affects either strategy, it decreases loyalty (customer captivity) by increasing communication between North Korean people and the outside world. In the long term, I think tourism weakens North Korean decision-makers’ strategy without helping it much, if any, in the short term.
North Korean decision-makers understand this risk, as evidenced by the tight control they put over tourists, mainly constraining us from communicating with them. The one product they confiscated at the airport was cell phones — not computers, books, currency, alcohol, or related things. The people most restricted are journalists. Cell phones and journalists aren’t physically dangerous. They convey information, the main thing that weakens their citizens’ loyalty by contradicting the stories they tell to create popular domestic support.
Next: starting points for change
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EDIT: I included much of this post and this series on strategy (edited and polished) in my ebook, Understanding North Korea: Demystifying the World’s Most Misunderstood Country. I wrote the book to help increase understanding, communication, and freedom.