I've always done this naturally, some days I read a blurb about some technology I used to use and realize, huh, I used to do that all the time but haven't touched it in years.

I think one of the key things is to have a passion for learning. I've always been bored doing the same thing over and over. Learning new technologies, design patterns, architectures, skills, etc is what interest me. That also, coincidentally, is what keeps me up to date and productive.