Check out DrupalEasy around the web:
DrupalEasy is the collective expertise of Ryan Price and Michael Anello, who joined forces to provide training and consulting services worldwide. Read all about them and what they can do.
Drupal is a free, super-powerful content management system for sites that require information posting and collection, including blogs, forums, videos, photos, and databases of information. We think it is the best platform available. Here's why...
More and more savvy organizations are going with Drupal for content management, and its no mystery why. It’s free, flexible, and easy to maintain for small or large volume sites. Learn more...
Anytime you write a Drupal module, you should always have the Coder module installed and enabled to check your code when you think you're done.
I'm tempted to end this QuickTip here, as that's all you really need to know.
The Coder module provides a code review for your code - it checks for common security issues as well as adherence to the Drupal Coding Standards. It's a snap to use - just click on the "Code review" link for your module on the admin/build/modules page and be humbled by how much smarter it is than you.
I prefer the "minor" mode - using this, Coder finds every little thing from extra white spaces to phantom tabs. Only once I get a clean Coder report do I consider modules I write "done".