Where I work, we have some bigger clients where we have some advanced integration systems with their accounting systems, stock control, exports to old windows systems, and the list goes on. So these things are not something we want to (or in many cases can) run on the dev version of the site.
To keep things still in version control, and not having to turn things off when dumping in a fresh database copy, we use the $conf variables in settings.php
The file settings.php is not checked in in git, and this is also where we automatically turn off js and css aggregation, by for example setting
$conf['preprocess_css'] = 0;
And some other stuff. But we also add our own variable.
$conf['environment'] = 'development';
This way we can do a check in the top of all integration functions:
So keeping this in our production code, ensures that integration functions are not run when developing on a dev site. Also, a lot of cron functions are moved to a separate drush command, and run by the server cron instead of implementing hook_cron(). This will then never be run on the dev site.
I am sure everyone has their own way of doing similar stuff, so please feel free to share your similar tricks, or improvements, in the comments.
I guess this calls for a transport related animated gif: