Applying for a PhD is a little more difficuilt than your usual masters or bachelors degree. First of all you need to decide which university you want to pursue it from and whether that University offers PhD in that particular program or not. Now after applying different fields may have different requirements but what is common amongst is all is the expectation to work by yourself. Hardwork, regularity, focus, commitment are all such qualities that will be needed regardless of your area of research. Candidates must also read the research papers of other scholars and the faculty of the university they are applying in. Sometimes you would also have to contact the faculty members so be careful while messaging or mailing them as they frequently recieve such messages so find a way to stand out and get their attention.