Letters of recommendation for grad school applications

[Miviato]

I understand the importance of letters of recommendation for grad school applications.
My question is: ideally, how much should my recommender know about me? I ask this because I study in a top, big research school in which the interaction between the undergrad researcher and the PI is very limited (as opposed to smaller universities): the professors are always busy - classes, conferences, travels, advising their usually large number of grad students, personal life etc, and there isn't much time for undergrads (who rely more on the other grad members of the group for help and assistance, and only occasionally meet with the PI).
Appreciate any inputs!

 

[Pyrrhus]

The best letters of recommendation come from projects you have worked as undergraduate research assistant. I think second best should be letters in top courses where you were very good, and the professor likely took notice of this.

 

[Choppy]

A reference letter will generally answer questions along the lines of:
- What is your own academic position?
- How many students have you mentored/taught/evaluated or otherwise observed recently?
- In what context do you know this particular student?
- How long have you known this student?
- How does this student rank within his or her peer group in terms of intelligence/creativity/research potential/background preparation/teaching skill/etc.?
- Ultimately would you recommend this student for graduate studies in our program?

There is no threshold for how well a referee should know you. But you have to think about the types of questions that I've listed above. Is the referee going to be in a position to write something positive about you? Is the referee in a position to make a fair call on the matter?