Best tip ever Paul - having your own personal website where you can try out new styles, programming techniques or even just write about them is critical for a young designer. Or old ones! I don't use my personal site that much anymore (I'll revamp it after the wedding) but it was more useful during my first few years than any book I ever picked up on css, actionscripting, design, usability or anything else. You'll find new things to experiment with over time - I'm going to redo the portfolio section of my site as an excuse to tinker with django and blueprintcss.

It's a bit dated but there's a good book on the topic by Joe Shepter called "Personal Web Sites: Top Designers Push the Boundaries with Experimental Design and Graphics" - Amazon link: http://tinyurl.com/3wxy7h