Are there coding standards I can follow when writing my Craft plugin? I eventually figured out that I could use a code sniffer in Sublime Text, load up a CodeIgniter rule set (not a Craft project, obviously), and see in real time where my formatting, spacing and naming conventions could be improved for consistency.

Is there an equivalent standard for Craft/Yii? I'd like to start forming good habits, and the Sublime Text part is a bonus but not required—I'm most interested in whatever standards there are to reference.
I would strongly suggest that you follow PSR-2 since that is what most of the craft source code adheres to and it is a pretty good standard for general PHP development. Just be aware that craft itself won't pass PSR-2 linting because there are places where it deviates from the standard, two of which are namespacing (craft has a global namespace) and indentation (tabs over spaces) but that is totally fine in my opinion. 

Writing clean, readable, intuitive, and testable code should be the end goal of any developer and if that means you have to violate a standards rule here or there, go for it: )