When people see you having fun building your business and you are making money they'll think very serious about joining you. Surround yourself with successful people. You want people who share common interests, common goals. Seek out people who are acknowledged leaders, learn from them, hang out with them. The challenge you face in building a successful business, is to constantly look for ways of raising the self-esteem of the people who join your network.
Motivation is the key, it comes from within.
It's the difference between giving someone a fish or teaching them to fish. When people first start sharing the product and the opportunity with other people they already have a certain degree of enthusiasm. No matter how much enthusiasm, you give away you always have more. That's because enthusiasm come from within. Network Marketing is a system where you can earn while you learn.