This is one of those posts that there's not a cut and dry solution for every situation, but rather recommendations based on feedback from hiring professionals and potential employees. It happens often enough that I thought it worthy of a post.
It is commonplace in most professional industries to use your full first name on your resume, cover letter, website and other career materials. Some even use the middle name initial or "junior, III, IV," etc. The main idea is that people think it makes them sound more professional or that this is what you must do in business. I disagree as all it does is confuse the hiring personnel along the way.
A resume is not some legal document, it is first and foremost a marketing piece for your career. You do not have to state your complete name on it, period. I'm talking here to people who don't go by their full first name in day-to-day life. If everyone in your life, including your co-workers call you Jim, then it is pointless to put your name as James on your resume. It just confuses people once they talk to you during an interview.
A resume is not some legal document, it is first and foremost a marketing piece for your career. You do not have to state your complete name on it, period.
The middle initial is also completely unnecessary. Adding it just adds one more piece of information to obscure your name in the pile of applications. Hiring personnel should be looking at the name you are going to be going by every day at work. Are they going to be calling you James R. every day? Very unlikely. The only person who seems to have that going for him is ESPN analyst Steven A. (Smith), and it still seems really silly in my opinion when others on the network call him Steven A.
Perhaps you have a very common name like John Jones. You think a middle initial will help differentiate you from the others. But the truth is the odds of there being another applicant with your same name is slim. A better way to handle a common name, if you must do something, is to either include your actual middle name (not just the initial) or go to first and second initials and actually go by them all the time. So if your name is John David Jones, go by JD Jones.
Using "junior, III, IV," etc. should not be used except in very specific circumstances. No one in the position of hiring you is interested if you are the second, third, or fourth James Robert in your family. The only exception here would be if your father or grandfather is/was a well known superintendent and you have the same name. Then it would be helpful to use the suffix.
In the end, you want a name on career materials that sounds approachable and comparable to how others in the workplace are addressed. Let's take our example from before -- Jim Davis sounds much easier to remember and approach than James R. Davis.
After reading this if you still feel strongly that you must have your entire name on the header of your career materials, then I strongly suggest you sign your emails, cover letter, and any other direct correspondence to the hiring personnel with your preferred name.