What should be taken note of in collaborating with professors/ researchers?
If this is your first real experience of research, please use this as a way of getting your feet wet, and learning how to do research.  I would advise against advocating for co-authorship with the professor in the early stage.  It could be seen as counting your chickens before they're hatched, or as a way of asking the professor to count his/her chickens before they're hatched.

Edit: I suppose you could let him know that you actually have a third objective which you forgot to mention -- to get a co-authorship.  But try to come across as ambitious and eager, rather than arrogant.  You said a primary goal is to get a strong reference for grad school.