Fine question!

Meticulousness, dedication, aptness and willingness to work hard! 

When supervising students' theses, I prefer hard worker and dedicated students.

High requirements. Don´t forget, they are young people with all the usual faults. Let them time for development.

Dear Abedallah M Rababah , You asked very nice features for PhD students.

I agree with Kamal: basic foundation knowledge in his field, critical thinking, communication skills, dedication, ambission, and hard working are basic requirements. I would add, however, love for what you do and natural talent.

In addition to the previous suggestions. In my opinion, is to be an open minded and deal with creative thinking.

Dear Jenan, do you think that "open minded and deal with creative thinking" may fit with "love for what you do and natural talent"?

Yes of course, Directing love and natural talent with good methodology, is what I'm talking about. love is not enough and natural talent needs refinement.

A research student should be hard worker and dedicated to her/his research.

Basic knowledge in his/her core field of research, critical and reflective thinking, analytical skills, writing and communication skills, learning attitude, cooperative, capacity to understand others' researches, and hard working are important.

A good researcher student is first of all ought to be honest with self & with others.Then come other attributes such as good brain, readiness for hard work, diligence, cooperation, precision science-wise & language-wise, self-confidence not amounting to arrogance, and respect for those supervising the research.

Persistence and hard working. A student researcher, when doing her/his research is looking for tructh.

Enthusiastic, intelligent, good at communicating with other people and ready to take criticism from the supervisor, journal editors...

A very important feature, able to accept critiques. Good point dear Tiia.

Hard and Smart Work.....

Dear Brenda Jacono 

i agree with you even all these qualities are not present in the student checheur but essentially it is to meet its features

Good point from Dr. Brenda Jacono. However, readiness for hard work (no. 3 quality in my above contribution) includes readiness for learning & not just for experimental work. The supervisor can use the method of my supervising professors (every nearly 3 months, I was asked to give a concise written report which was evaluated & commented on). This way the student is judged ( Is  there  improvement or  stagnation or deterioration?). 

I think s/he should be open-minded and accept critics for her/his improvement.

I think that communication skills are essential, too.

I don't think that communication is a required feature of a research student.

Sponsored by Microsoft Research, Student Research Competition - an internationally recognized venue to enable research students, expects them to

http://src.acm.org/about.html

I may add another feature, that is needed by the student (and not from the student) to become a good researcher, which is: a reasonable research project when suggested by a supervisor that can be done in the university in adequate time. I remembered now the story of a friend of mine who went to a Middle East university to get M.Sc. in organic chemistry by research. He was given a project that needed unavailable materials & equipment & he was told to wait, at least, 3 months for their arrival. So he switched immediately into his second favorite subject (analytic chemistry) & obtained M.Sc. and then PhD. I mean we cannot only blame the student. Sometimes or often , those responsible in the university are to blame when there is no good research.   

I think researcher must be very active as well for his/her research.

Dear Mohamed Dallel,

Self-confidence during the preparing stage. 

Accept challenges and work on them.

Open your mind for new research.

Expand your research network ( attend conference, workshops, online courses)

Evaluation your Knowledge and your research through discussion groups.

Enhance your academic skills.

Exchange knowledge with other researchers.

Best regards,

Honest, unbiased, and should engage in high quality research only.

Good question and Informative answers thank you all

scientific writing skills

According to my long experience (over 40 years) the best students are curious, hard working, asking good questions, are not discouraged by failures, they repeat their experiments with appropriate controls. Good students are open to critics, they like to share knowledge with other students (in the lab or different labs in the department), they like to cooperate and they are respectful to the staff.

All the points mentioned are very important. However, i believe the will and determination to work hard overrides the others.

Motimation and self-studying