ERP projects are among the most critical efforts IT ever undertakes, as they touch almost every part of essential business operations and are complex technically. Not surprisingly, some fail -- spectacularly. Although ERP has been an enterprise focus for a decade, many companies are still embarking on such efforts, and even more are dealing with ERP redos because of mergers and business changes. Here's what you can learn from the failures of others and put to use on your own ERP projects.