There are some tough calls to be made for sure, and a lot of moral judgments and ambiguity. Personally I keep a few guidelines in mind:

- Just being a decent person. Making sure that I'm not acting entitled. Being aware of different norms and being accommodating of that. Just basic stuff.

- Not engaging in voluntourism, i.e. volunteerism that is more of a burden than a help. If I want to help, I donate to an organization instead.

- Not supporting services which rely on the commodification of animals. More often than not, these animals are being mistreated, and this treatment is often deliberately hidden from clients and thus even more difficult to identify. No animal exists for my personal pleasure and entertainment, and I don't need to be supporting that.

- To the greatest extent possible, not supporting businesses which engage in human rights violations or the commodification of people/cultures. Indigenous cultures in particular tend to be commodified for tourists. Sex tourism is an obvious one to avoid. Anything that turns people and their lives into zoo animals or objects, or that directly endangers them for my benefit, is something that I have no business supporting.

- Being aware of environmental impacts. By far the easiest way to do that is to limit meat consumption and to minimize travel by plane, especially short haul flights (the train is better anyway). Those two things have a far bigger impact than anything else I could do, and I don't need to go too far out of my way for them.

The "boycotting countries" issue is a minefield in and of itself. It's often a bigger statement to go/not go somewhere when something is escalating and in the news, such as going to Russia right now, or going to Myanmar last year. Ultimately though, visiting a country does not equate to an endorsement, and it's nearly impossible to avoid indirectly supporting some forms of oppression, even when you aren't travelling. There are also marginal benefits your presence might bring, as is generally the case when there's more interaction in the world. All in all though, I'm not generally of the boycott mindset.