One of the best sessions I’ve had so far was CSS For Grown-Ups by Andy Hume.

Some of the highlights:

• CSS is ‘Constraint Programming’.
• Obsession with eliminating ‘classitis’ is outdated and not good practice.
• The idea of doing a redesign without touching the markup is a myth.
• Apply OOP principles to CSS. For example, extend your semantic classes, such as .promo-box–light (double dash indicates dependence).
• Optimize for change! Website maintainability is supremely important.
• Using semantic class names is emerging as new best practice.
• Selector Queries Andy’s JS solution for adjusting elements based on width using a data-squery attribute and adding classes.
• Use surgical layout helpers, eg .gutter-left, .gutter-right in div containers.
• Don’t style pages, style modules.
• Do styleguides in code, ala Twitter Bootstrap or Paul Robert Lloyd’s Styleguide.
• Style guides are a great opportunity to bring design and dev together.

For a more in-depth overview of the talk, check out this blog post along with the slides.