It is not as if these were passed down from Mount Sinai, but they are still pretty darn important for any Drupal based project or website. Here are the three commandments that govern any work that our teams do with Drupal. Doing so increases quality, and minimizes costs (something that we know our partners appreciate in this economic climate).

• Thou shall use as much of the Drupal Framework as possible before ever writing code (Core & Contrib). These days, Views and CCK should always form the basis of any Drupal deployment.
• Thou shall do things the "Drupal way". If it takes you an extra 1/2 day to learn something new, or an extra 1/2 day to contribute a patch back to Drupal for Core or a Module -- do it. In the long run, this will give clients a BMW versus a Ford Metro.
• Thou shall be responsible for your own knowledge and expertise of what Drupal modules are available and how they can cost effectively provide value to clients. There is a drupal custom module for most common business logic. Obey thy Drupal commandments. Or feel the wrath.