What are your suggestions for dealing with the growing problem of "over-tourism" that some popular destinations around the world (Kyoto, for example) are facing?

In Japan's case, stop hyping Kyoto.

There are lots of possible ways to deal with it by making places less convenient such as making places only accessible by applying in advance, increasing the price of tickets or gating off certain areas and making people pay a fee to enter.

However, I think that if tourism were to be spread out more, it would have more positive results. Maybe someone can make a sightseeing comparison guide that can recommend other similar places by search criteria. The alternative places would be in lesser known cities, but still accessible by public transport. So for example, if people like visiting Kyoto for the atmosphere, maybe another city like Inuyama might pop up. It could help spread tourism a bit more.

The Galápagos Islands restricts the daily allowed visitors. It is easier due to the remote nature and limited modes to get there.

Machu Picchu also restricts the number of daily visitors.

Different hiking trails around the world also have daily limits for the numbers of people allowed.

People who visit these places are happy with the restrictions since it helps keep the human impacts down. For urban locations, I've only seen front-entrance restrictions that didn't apply to locals. For people jetting in, "hitting" the spot for 2 hrs, and leaving, those restrictions are easy to control by having the tour companies draw for the available daily spots. For longer term visitors, they would quickly learn that entrance by going around the corner is unrestricted. The first step for these urban locations is to accurately count the tourist visitors. Nepal does this at many of their World Heritage sites.

Hot spots are fads, eventually they will be replaced by the next "must see" destination. The focus does need to be on how to protect the areas that are visited and make sure no lasting damage is done. Perhaps educate would be visitors on how to respect and preserve their host city/area of interest?

Don't call it 'over-tourism'. I really don't think you can do much about it, except (in my case) avoid going to those places. As far as my travels all over Japan are concerned, once in Kyoto for a few days, same for Nara, a day in Matsushima Bay, a simple day or two for transportation connections in Tokyo, and I'm off and away to places where I don't see a lot of other tourists. But, I like Japan for the culture of its people, not the same-old, same-old temples and castles.

As for other countries and cities, my travel philosophy's the same. Get away from the traps and trappings, and enjoy the people. Live their life for awhile.

I think many people would love to play a part for a good cause. If they're made aware, most would voluntarily do the right thing. To add what others have suggested above, educate people especially from majority visitors origin countries, price hikes in peak seasons, rebates in low seasons, quota-ring, rotational itineraries within tourism spots. Generally , just a good management data system cascading from head to tail would help mitigate the conditions.

Agree with Trevor, don't consider over tourism as a problem but as a blessing, you just need to channel that volume of people elsewhere or create limitations to how many can a destination can accommodate at any given day. You should actually be happy that a country gets a lot of tourists, but then again, all things come with their downsides. Japan has lots of beautiful tourist destinations from Hokkaido to Okinawa but only a handful of mainstream spots get recognized. its time to open up and develop those other tourist destinations

Massive billboard campaign in tourist areas with say William Shatner or Albert Einstein’s face telling tourists to “get a life!”

Simple. There needs to be a limit on the amount of Chinese inbound tourists per quarter. Easily 90% of the tourist congestion in places like Osaka and Kyoto are caused by Chinese tourists.