Choose locally owned accommodations so your money goes back into the host community. Check out Airbnb, VRBO, Eco-Lodges, etc. If you stay in a hotel, pick one with comprehensive sustainability goals.
If you have the ability to spend more time at each destination and take less trips, especially flights, you will be able to minimize your travel emissions. This is also an opportunity to learn more about the local community you are visiting.
When possible, use public transportation, trains, bikes, or walking to get around when traveling. Avoid short flights and individual vehicles.
Buying souvenirs is great way to remember your trip, but make sure to buy from local artisans and not trinket shops. This ensures your dollars will go directly to artists and you're buying high-quality goods.
Although you might have great intentions - traveling to volunteer often disrupts the local economy, doesn't account for the needs of the community, or encourages the "white savior" complex. Instead, travel to learn from other cultures.
Flying food across the world means a bigger carbon footprint, so focus on eating locally grown and in-season food. Try to stray away from the tourist hubs to support smaller restaurants.
Individual actions make some impact, but the change we need for emissions to hit net zero by 2050 to limit global warming, will need to be systemic. The best thing you can do to support this is vote for elected leaders who have a comprehensive climate strategy.