There are so many tools out there to use, it's really easy to get distracted and not really know what to use. For a long time I just use Compass to compile my scss files into CSS, but there is so many other things you could be doing too. So when I discovered Gulp, I started to use it, and it helps a lot when I'm theming.
One of the first things that I do when I start a new project is to configure my environment as development, to react on what I'm doing, specially when I'm theming. Disable cache, enable debug messages and more. These steps are among the ones that I always do:
Go to the sites/ folder of your project and copy example.settings.local.php to the folder like this: cp example.settings.local.php default/settings.local.php (renaming it to settings.local.php in the process).
Handling media in Drupal has been … let’s just admit it .... horrible. Even in Drupal 7, the Media module didn’t really handle media very well. The only module who came close was Scald, but it was a cumbersome module to work with and required quite a skillset to install and configure.
So, Drupal 8 is the new kid on the block. And whoa, is that the most popular person on the prom! The three major things (and there are hundreds more) that I like about D8 are the fact that you can (and should!) control all Drupal downloads with Composer. Everything else is just crazy. And the other two things are Configuration Management and Drupal Console.
