1. Use a KPAP-approved tour operator
2. Climb with properly trained guides
3. Tip your mountain crew
Sometimes people ask why the industry doesn't increase salaries and do away with tips. A decent question. But tips aren't incorporated into salaries as mountain crews themselves like the motivation of receiving a potentially big tip if they give really good service. Also, they like to keep their wages below the tax bracket and then receive non-taxable tips as a way to supplement their income. Tips and the tipping ceremony are a way of honouring the hard work and support provided by the mountain crew. We've never met a climber who didn't want to tip their crew (and tip them well!) at the end of a climb. Depending on the size of your climb group, the overall amount that you need to personally budget towards your group's tips can be sizeable. Usually, the smaller the group, the heftier your personal contribution to the overall tip will be. Please include your tip amount in your Kilimanjaro budget. You can learn more on this topic in How much does it cost to climb Kilimanjaro?
4. Adopt eco-friendly trekking habits
Stay on the trail
Be thoughtful about going to the toilet
Follow the Leave No Trace principles
5. Support the local economy
6. Support local conservation efforts
7. Be a respectful tourist
Learn a few local phrases of Swahili to show you're willing to make an effort. It's especially nice if you can use local titles of respect for elders. Really listen to locals and ask respectful questions to learn more about their story, and so on. Refrain from making any vocal criticisms about local habits, situations and so on in public. Make an effort to learn about the local custom around tipping (not just relating to your Kilimanjaro climb, but in other environments too). Read through Kilimanjaro National Park's rules and stick to them, whatever your opinion about their validity.