Something I've only just discovered the usefulness of is code templates in Netbeans. I always used to have autocomplete set up in Outlook for common phrases like "if you have any queries, please get in touch", and saved a lot of typing. Having found the NetBeans templates module for quickly creating common bits of Drupal code, I started digging around in the default NetBeans options, and found that there are all sorts of little timesavers. Here are a few good ones:
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It's a good idea to theme the error pages on your site. It looks more professional and provides a better experience for your users. A lot of people have a soft spot for the Twitter fail whale. Some people really love it. You can also add functionality to help keep your visitors on the site when they get an error.