What is required to achieve Nirvana in Buddhism? Nirvana is considered by many religions the pinnacle to strive for.  What do I need to do to achieve Nirvana?  Are there different perceptions of the requirements held by different sects?
To answer your question let me draw an analogy. What is required to become a professor?
According to Wikipedia, "A professor is a highly accomplished and recognized academic, and the title is in most cases awarded only after decades of scholarly work to senior academics". Being a professor is not a concrete state, it is a label they put on years of hard work, culminating in professional realization.

Similarly, Nirvana is not a concrete state, it is a common name for the condition of a highly accomplished spiritual practitioner. This condition is not something you can contrive knowing the requirements, it is a result of years of personal transformation.

Nirvana can be characterized as condition of having transcended suffering &amp; death. The requirement for this is said to be a complete cessation of Attraction (obsessing over something as desirable), Rejection (obsessing over something as undesirable), and Ignorance (mistaken understanding of how everything works). One of the key components of Ignorance is a deeply lying conviction in existence of substantial self and a tangle of reflexes that grow around that. Much of Mahayana practice is targeted at destroying this belief, not just at conceptual level, but at the level of basic day-to-day instincts.

If we could simplify the requirement for becoming a professor to "complete cessation of ignorance in the field of study one specializes in", we could perhaps make a stretch and define Nirvana as "complete cessation of ego complex, along with negative experiences and behavioral tendencies it generates". As any simplification, this is not entirely accurate: just as becoming a professor requires tons of practical skill and experience outside of the primary field of study, attaining Nirvana requires cessation of all mental and emotional obscurations, a tendency to get stuck on anything, not just on self.

Now, for the purposes of this discussion I'm equating Nirvana with Enlightenment, which depending on a school may or may not be the right thing to do. Specifically in Mahayana, Nirvana is considered a conceptual projection (a shadow of ego so to speak) that has to be transcended as part of awakening to Self-Existing Buddha Nature (=Enlightenment).