Ifeanyi Onwe, a sophomore at the University of Pittsburgh, likes to plan his classes ahead.

A year ago, Mr. Onwe, who is interested in biology, was ready to take a laboratory class for organic chemistry the following spring.

But at the University of Pittsburgh, students were required to see their adviser before registering. He saw his adviser later than some other students. By then, the class was already booked.

OK, he thought, I'll try again next semester.

But his fall term advising meeting came in March, later than for some other students. He she was shut out of the class again.

Scheduling can be a complex -- and aggravating -- process, even for returning students. It's often up to students to make sure they do not have to take additional classes during the summer, or worse, pay tuition for a fifth or sixth year.

All colleges offer help. Many universities have an advising system to keep students on track to graduate with their desired majors on time. Some require face-to-face meetings with advisers; some use course sheets and checklists to be filled out each semester; and some offer online systems where students can check their academic progress.

"We have everybody here at their disposal; they just have to ask," said Jacqueline Connolly, director of registration for the South campus of Community College of Allegheny County.

Course registration often starts many months before the start of a term, often in a staggered system where upperclassmen (or honor students or athletes or other select groups) can choose their courses earlier than other students.

But students often wait a while before they decide what classes to take. At CCAC, the peak periods for course registration generally occur just before classes start, Ms. Connolly said.

For underclassmen, the main penalty for waiting until later to register -- such as not finding a seat available in an already-full class -- is not as damaging as for upperclassmen.

Underclassmen often take many courses to fulfill general education requirements.

If the freshmen or sophomores cannot take a certain class, they likely will be able to take another class to satisfy a general education requirement.

But for upperclassmen, a shut-out gets dicey.

Majors sometimes require students to take classes in a relatively rigid sequence, where an advanced math class can be taken only after certain pre-requisites are taken in a prescribed order.

And some classes required for a major are offered in only one semester.

For Duquesne University students who are trying to graduate with a major in communication and rhetorical studies, there is only one opportunity a year to take two of the required courses: history of communication and communication ethics, said William Klewien, an undergraduate academic adviser.

History of communication is only offered in the fall, while communication ethics is only offered in the spring. Both are generally taken during the junior or senior year.

Even for underclassmen, taking the wrong introductory class can mess up sequences for later in college.

For instance, there are different types of calculus for different tracks. For those pursuing, say, a humanities degree, the calculus class they take may be less rigorous than the intensive calculus class a mathematics major must take and different than the calculus with business applications an accounting major must take.

If a student changes majors from English to math, or from apples to oranges, the student may have to retake calculus, this time in a different track, to satisfy requirements for graduation.

The delay in taking the wrong introductory calculus class may cause a now-prospective math major to delay taking required higher-level math classes, she added.

(The original basic calculus class often would still count for elective credit, however.)

Advisers said students should keep track of the courses they need to take to graduate with their desired majors, and they should use, above all else, common sense.

Some advice:

• Many schools require students to take around 36 to 42 classes to graduate. Students should compute how many classes they need to take each term to stay on track, usually five or so classes per semester.

• Students should take general education courses that might be used for various majors. This allows them to be flexible.

• Students should take classes they can be awake for. A night person should think twice before taking 8 a.m. classes.

Colleges sometimes try to offer increased advising to students who go off track.

Some have alternative means of graduating on time. For instance, though rarely, West Virginia University officials recommend its students switch to a recently created multi-disciplinary studies degree to graduate on time if they have taken enough courses to satisfy the requirement for three minors, Anita Mayer, director of undergraduate advising services at WVU, said.

But if all else fails, taking summer courses or fifth year may be necessary. For the additional classes, advisers recommend taking community college classes when possible because they are generally cheaper than those at other schools.

Mr. Onwe, of Lagos, Nigeria, said he still believes he is on track to graduate on time. But the setback did force him to take alternative courses he is "not really into."

Pitt is introducing a new system for returning students to register, said Mary Beth Favorite, acting director of the advising center for the School of Arts and Sciences. Online registration will be used for students to register for classes on their own. But they will still need to meet with their adviser before registration starts.

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