How to interview undergraduate candidates for research assistants? I am at a public high-ranked Canadian university where undergraduates are heavily encouraged to participate in research, and currently recruiting an assistant for myself (and my supervisor). While at this university both as an undergrad, undergraduate researcher, visiting lecturer, and graduate researcher I have seen a very large variance in undergraduate performance:


A good number of students have great research potential, motivation, and creativity; these students typically contribute well to undergraduate research and go on to top graduate schools in their specialties.
A good number of students are here just to prepare for a professional school (typically Med School, but sometimes Law). Typically these students are very hard working, but don't have a passion for research. They apply for research positions just to flesh out their CVs. They typically don't display great creativity and tend to be overworked and over-committed.
The majority of students are hard to motivate, and seldom display great research potential or creativity. It is hard to get results from them on tasks that are not route/mechanical in nature.


Are there any tips and tricks to how to attract students of type 1. More importantly, how can I structure interviews to better recognize students of type 1? Is it impossible to attract type 1 students with high probability and I should just hope for the best, but plan for the worst? Is the division I observed artificial and it is my job as the supervisor to turn every student into type 1?
My advisor, bless his heart, entrusted in me the responsibility of interviewing and selecting undergraduate students to work in our research lab while still being a graduate student myself.  Sometimes it's difficult to determine what a person is really like just from a few minutes speaking with them.  I found a few particular questions to be particularly helpful:  


Ask them what their goals are for the future.  Most undergraduates give very general answers because they are not sure what they want.  A highly motivated student knows what they want, and are likely to link their goals as part of the reason why they want this particular research job opportunity.  
Ask them to describe in detail a difficult problem that they had to overcome, and explain how they overcame it.  This is a question they typically anticipate, but it's the manner in which they answer that matters...  Observe how well they put together their answer, how long it takes them, and how well they articulate it and its relevance to the research job that they're applying for.
Ask them about their greatest strengths, and greatest weaknesses.  In particular, examine how they explain how their weaknesses may affect their job and how they intend to overcome these weaknesses.  A strong candidate will not only be self aware and honest, but will seek ways to overcome these deficiencies.