A third key to achieving the summit of Kilimanjaro is to be acclimatized as one ascends the peak.  The process of acclimatization is different for different people and there is no telling how each person will be affected.  It's important to take the time to stay at higher elevations for awhile to prevent altitude sickness.  The hiker should choose a route that allows him/her to acclimatize in stages and for some periods of time while ascending to provide the best shot at making it.  The climber can also prepare by ascending other high mountains before the trip to test one's ability to withstand the thin air.  There are also medications such as Diamox that allow the hiker to tolerate higher elevations more easily. 

Another important factor leading to not being left behind is to be medically prepared not only for the African environment, but for the Kili environment.  Acquiring all the necessary immunization shots before the trip protects one from being knocked out of the box by diseases such as malaria or even the flu.  It would be a shame to be totally mentally and physically prepared for the climb only to be derailed by an unsuspecting medical problem.  Get a full medical and physical checkup prior to the climb and if older, perform these checks long before and just before the climb.  Also, make sure to pack a thorough personal medical kit to be prepared for any medical threat you have familiarity with.  Cancer survival also heavily depends on the medical tools one has at hand.  Understanding side effects and how to treat them allows the survivor the best chance of success without being thrown off course. 

Finally, since Kili subjects the climber to a wide spectrum of weather conditions, the successful climber carries a complete portfolio of clothing.  The summit can be under Arctic conditions requiring the hiker to bring winter gear.  Layers of clothing provide the best approach so as to endure the low summit temperatures as well as the heat of the lower elevations.  Rapid changes occur as one ascends or descends a lot of elevation.