1. What are some of the unique traits of Mahayana Buddhism?
For one, in Mahayana Buddhism enlightenment is seen as attainable by all, not just monks and nuns. Mahayana is also more outward-directed, focusing on compassion towards others rather more so than individual enlightenment. It also centers around the concept of bodhisattva, beings who defer entering Nirvana in order to help other sentient beings to reach enlightenment.
2. What is necessary in order to attain bodhicitta?
The most essential condition is the desire to attain Buddhahood.
3. Why do you think Mahayana Buddhism appeals to such large numbers of people?
I think the salvation-oriented message and the involvement of the laity is attractive to many people. The need to abandon normal life and live a monastic one (as in Theravada) is a step few people are willing to make. Also the emphasis on compassion towards others and universal salvation is appealing to more collectivist East Asian cultures than is the individualistic approach of Theravada.