As the founder of one of the most successful companies in the world, Facebook CEO Mark Zuckerberg has revealed what he looks for in a prospective employee at the Mobile World Congress tech conference held in Barcelona."I will only hire someone to work directly for me if I would work for that person," Zuckerberg said on Wednesday. "It's a pretty good test and I think this rule has served me well."The 30-year-old Facebook CEO, who has a net worth of around $35 billion, provided other tips to create a successful company.Emphasizing that one of the most important things is to keep the team as small as possible, Zuckerberg also said that employee's values should align with the company's and added:"The most important thing is to just have faith in yourself and trust yourself. When you are young you hear that you don't have the experience to do things, that there are people with more experience than you. I started Facebook when I was 19."