<p>^There’s no hard fast rule to how much research you need but I’d say the more the better. Definitely someone doing 3 years of research including summer internships has a significant advantage over someone who has, say, one summer’s internship experience. </p>
<p>I don’t think there’s an average for how much research students at top schools do. Its pretty common where I go for students to start either their sophomore or junior year. </p>
<p>Yes you’ll usually go to the grad student for help not the prof. The professor is there not to guide you through every tiny thing but rather to check up on you and make sure that everything is going well. A good professor is one who continually makes sure that his undergrad student is learning and benefiting and frequently touches base with him.</p>