1. The first author should be that person who contributed most to the work, including writing of the manuscript.
2. The sequence of authors should be determined by the relative overall contributions to the manuscript.
3. It is common practice to have the senior author appear last, sometimes regardless of his or her contribution. The senior author, like all other authors, should meet all criteria for authorship.
4. The senior author sometimes takes responsibility for writing the paper, especially when the research student has not yet learned the skills of scientific writing. The senior author then becomes the corresponding author, but should the student be the first author? Some supervisors put their students first, others put their own names first. Perhaps it should be decided on the absolute amount of time spent on the project by the student (in getting the data) and the supervisor (in providing help and in writing the paper). Or perhaps the supervisor should be satisfied with being corresponding author, regardless of time committed to the project.
5. A sensible policy adopted by many supervisors is to give the student a fixed period of time (say 12 months) to write the first draft of the paper. If the student does not deliver, the supervisor may then write the paper and put her or his own name first.
ref: http://www.sportsci.org/resource/writing/author.html
