Sometimes, the order of names is alphabetical. Sometimes, the first author is the person whose contribution was greatest. Interview former students. Students who have graduated are more likely to answer your questions candidly than current students. Ask a potential advisor for names and e-mail addresses of former students, whom you can contact.
Many projects suffer unanticipated delays.
When you work closely with someone else, disagreements are inevitable. The key question is whether conflicts were handled respectfully, with satisfactory resolutions. If you have a major conflict with your advisor, first attempt to find solutions within you department, consulting another trusted professor, other members of your committee, or the department head. Should you be unable to find a solution by working with people in your department, be assured that we in the Graduate College are available to help mediate conflicts. Fortunately, major conflicts are rare.