Climbing Carstensz Pyramid is the only of the Seven Summits which specifically requires technical experience before summiting. Although this is not a particularly difficult climb, you must be familiar with scrambling, working with fixed lines, rappelling and jumaring. You should be comfortable with routes of a difficulty up to 5.7. Many tour companies offer short, alpine courses which help you to gain skills and confidence in technical mountaineering.
In addition to technical proficiency, you will need to build your strength endurance as well as your cardiovascular capacity. Remember that being fit enough to run a marathon does not mean that you will be able to handle the challenges of a high-altitude peak. This is because pure aerobic fitness is not enough. Your training regime should focus on all of:
Climbing conditioning: walking or hiking up hills or stairs carrying packs up to bout 40 lbs
Strengthening exercises: for lower body and core. This includes sit-ups, squats and lunges.
Cardiovascular workouts: Aerobic and anaerobic, including cycling, running or swimming.
Flexibility training: this decreases your chance of injury
Off a relatively solid baseline fitness, you should start training properly for Carstensz Pyramid at least 3 months before your trip.
Typically, your training strategy should involve increasingly difficult work-outs by ramping up your workout time, distance and elevation gain by about 10 % each week. Be careful not to rush this process, as this may lead to injury or insufficient preparation.