Research that is poorly conceptualized or executed might be worse than no research experience at all. If a student does have a poor research experience, try to explain the reasons; a student who understands the causes of failure is less likely to suffer permanent career damage.
Your broader challenge is to interpret a research experience in the context of the student's total education. The primary purposes of student research are to master techniques, to learn to think critically, to acquire strategies for problem-solving, and to learn the importance of patience and perseverance in the unpredictable context of research.
An excellent source of information and support is the Council on Undergraduate Research (CUR), a national organization founded on the premise that research adds depth