There a several things to do as sson as you are accepted by a research mentor, to ensure a successful experience.
1. Have a meeting at which you ask your mentor what their expectations for you are. This includes numbers of hours they are expecting, the schedule of hours, how often you should have a face-to-face meeting to update them on your prgress, how oftern they want e-mail reports, if they want any products turned in (a paper, report, etc...). It is critical that you are on the same page with respect to what they are expecting and this must be explicitly discussed to avoid misunderstandings later. Share with them your expectations for the experience as well.
2. Keep the agreed upon schedule. Having a test or a paper due is not a reason to miss your research hours. Plan ahead and work around your other obligations. Your letter of recommendation at the end of the experience won't say you are dependable if you take off every time something else comes up.
3. If you don't understand something, ask. If something is explained to you - take notes and learn it so you don't have to ask again. This is a learning experience so treat it like any other - do your homework and learn what you need to do the project.
4. If the project is not meeting your expections, discuss it respectfully with the mentor. Maybe you have learned a techinique and are ready to do more. Maybe you would like to add another facet to the project. Be sure that you engage in open and frequent communication with your mentor.
5. Meet all deadlines given.