If you feel that you’re already competent, be prepared to produce a verifiable resume of your own successful high altitude climbs.
Some people have said that climbing Mount Everest is more of a lifestyle than a goal. The best way to physically prepare for Mount Everest is to live, climb, and train at altitude. You may consider moving to the Rockies or the Sierras a few months prior to your climb. Definitely take time off to do training climbs. Aconcagua in Argentina, or Denali in Alaska are two good choices. Even better are Cho Oyu in Nepal or Shishapangma in Tibet – two of the easier 8000 meter peaks that would help you condition your body to the demands that Mount Everest will exact.
Finally, you have to prepare yourself mentally for the challenge. From beginning to end, your Mount Everest adventure will probably run about 68 days. Seven weeks of that (approximately) will be spent on the mountain itself, but only 21 days or so will be spent actively climbing. The rest will be days spent acclimatizing, resting, waiting out bad weather, building up your energy, and resting some more. You’ll need patience, a constantly positive attitude, and the ability to be the epitome of a team player. With luck, your conditioning, skill, and good judgment under stressful conditions will result in a positive expedition experience and a safe return home.