What is the best cardio activity to prepare for my Kilimanjaro climb?

Hiking is the best possible preparation for your Kilimanjaro climb. If you’re a beginner, you should start by going for walks and carrying no weight with you. Gradually as you get more comfortable you can increase the duration of your walks, the height of ascension, and begin to add weight to your pack. You should also wear the boots you are planning to wear on your climb. Ideally, you should hike the kind of mountainous terrain you will be faced with at Kilimanjaro, but if that terrain is unavailable to you, you can try to simulate with stairs.