How can I utilize existing UI for my plugin's control panel views? I'm new to building plugins and I need to make templates for the control panel. How can I use existing Craft UI components to keep things consistent and save myself from having to rebuild everything?
Have a look in craft/app/templates for tons of great, easily-reusable examples that make up the existing control panel! They may not be documented, but there's a whole lot of quality stuff there.

You may also want to consider using macros from craft/app/templates/_includes (Craft TemplatesService doc, Twig macro doc), which will go a long way toward good DRY templates.

Bonus: this is also a great way to learn clever ways of doing things in Twig, like breadcrumbs for example. P&amp;T builds excellent stuff, so there's lots to learn from and steal whether it's for the control panel or the front end.