What is important is not how busy an advisor is, but what priority he or she gives to students. Occasionally an advisor will be out of town, or too busy to see advisees. But an advisor should make time, usually within a week, to see an advisee. Students should not expect their advisors to take all the initiative. Advisors will not usually contact students just to see how their term is going.
Students are actually much harder to reach than faculty.
Fellow students don't take messages reliably, and mail often goes astray. Students often don't realize how hard they are to track down. At the beginning of the relationship, it is an excellent idea for students to make a special effort to reach out to their advisors, making an appointment or two to ask questions about the advisor's research area, the Department's major research areas, and the theory behind the major requirements, etc. Your advisor is a better person to ask about these sorts of things than your fellow students or even graduate students. If you get to know your advisor well at the beginning, there is more of a chance to start an excellent advising relationship.