Climbing Mount Kilimanjaro is a physical undertaking, so you should prepare yourself accordingly with a Kilimanjaro training program. Being in good shape is important in many respects. Obviously, strong, conditioned legs make it easier to walk uphill and downhill for sustained periods of time. General aerobic fitness allows the body to function efficiently with less oxygen. And a fit body is more likely to withstand the stress of consecutive days of hiking and camping. Finally, a positive mental attitude can work wonders for you when fatigue and doubts arise.
How hard is it to climb Kilimanjaro? That's a difficult question to answer because some people don't train much and fare very well, while others engage in a disciplined training program and succumb to the altitude in a few days. We've heard marathon runners tell us that climbing Kilimanjaro is the hardest thing they've ever done. The best advice we can give is to train adequately, as described below, and get yourself in the best possible hiking shape. The mountain is a big unknown, and you won't know with certainty how you will react until you are there. In a survey we administered, on a scale of 1 (easy) to 10 (difficult), respondents rated their climb with an average difficulty of 7.
The best exercise that you can do to prepare for Mount Kilimanjaro is hiking.
There are training regimens on other operator's sites which entail strict, extensive, cross-training programs, featuring hiking, running, biking, swimming, weight training, etc. Do not be alarmed by this. Those programs are excessive and unnecessary to sufficiently prepare for climbing Kilimanjaro. The best and perhaps only exercise you need to do is to hike - period. After all, that is what you will be doing on the mountain. Ideally, you should try to hike as much as possible on hills or mountains to simulate ascension on Mount Kilimanjaro. Doing day hikes is superb training. For those who do not have access to trails, but have membership to a gym, you can train very productively on a stair master machine. If you have no access to trails or a gym, then try to walk as much as you can, with extended walks on the weekends.
You should start training for climbing Kilimanjaro at least two months prior to your departure.
If you've never hiked before, you should start with shorter time intervals, a slower pace, and no weight (in your day pack) and then gradually increase all of the above as your fitness level improves. Remember that on Mount Kilimanjaro, you will walk slowly for prolonged periods, and carry probably no more than 20 lbs in your day pack. Therefore, in your training, it is better to increase the time interval/distance and keep a slow pace than to shorten the time interval/distance and increase the pace. Try to train three times a week, for at least one hour per session, at a minimum. If you can do day hikes for four to six hours, with moderate elevation changes (~1,000 ft/305 m) while carrying a 20 lb pack, or if you can walk on a StairMaster for 1-2 hours, at 30 steps per minute while carrying a 20 lb pack, then you're probably ready for the real thing.
Your longest/hardest workouts should be performed two to four weeks before your departure. For the last two weeks, you should taper off your training and in the final days, rest so that your body has time to recover before your actual climb. In addition to walking/hiking, you can also supplement your training with exercises such as running or cycling, which will increase your aerobic capacity.
It is imperative that during Kilimanjaro training, you wear the boots that you intend to climb with so that they are sufficiently broken-in (to prevent blisters). Additionally, you should wear the day pack you intend to carry so you're your shoulders/back/hips get used to the points of contact and weight (to minimize chafing and soreness).
Lastly, physical training is just one part of getting in shape. If you have an unhealthy lifestyle, use the climb as your motivation to change. Eat more fruits and vegetables. Reduce your red meat consumption. Don't drink or smoke. Get eight hours of sleep per night. Don't worry. Be happy.