I think the most important skills Ph.D. candidates should develop are the ability to think critically, and to have a global perspective. These skills are important because they will be used throughout your professional life. 

Critical thinking is important in every field. It is especially vital for Ph.D. students who often work with little or no supervision, and must independently identify problems and find solutions to them. Critical thinking can help you to recognize and solve problems that arise in your work, and it can also help you to develop more effective ways of doing what you need to do. 

A global perspective is also important for Ph.D. students because they often work on projects that involve cooperation with others from different cultural backgrounds (e.g., other scientists). Having a global perspective can help you understand how people from different cultures see things differently; it can also help you learn about new ideas or ways of doing things that may not be familiar to you, but that could be useful in your own work. 

And then, if you successfully initiate your procedure, these are the prime qualities a Ph.D. candidate should adhere to.