"Write what you know" is the general wisdom offered to beginner writers, suggesting you start from your current base of knowledge. While that can be essential advice—especially to non-fiction writers, where expertise is all—as a fiction writer, I prefer to rearrange those four little words to "know what you write," which gives me the perfect excuse for trying new activities or learning new subjects. It all feeds into the fiction pot, if not in the current book, then maybe the next. It may not add much more than a few sentences to the novel, or may even just provide a trait for one of the characters, but there is almost nothing that can go to waste once it’s stored into the memory bank.
Travel provides locations and culture. Trying new sports not only increases detailed know-how of the specific activities, but can also provide interesting insights into the attitudes and confidence of other participants or spectators (not to mention providing the necessary zest to tackle the sedentary marathon of novel writing). Continued learning, whether academic or of a more practical nature such as first aid or CPR, not only boosts your knowledge, but can provide unexpected plot points as the number of threads available to weave into your story increases.
For a writer, one of the most fun ways to learn is to talk to people about their work. We may think we know what a person "does" for a living by the label applied to that particular profession, but how often do we really know what they do, why they do it or all the advantages and disadvantages of such a role? If you don’t know of someone in a particular profession that you want to include in your novel, it can take some courage to ask total strangers to give you insight into their jobs. But I find that most people like the chance to talk about their work and what it means to them. If you are willing to share a particular plot point with them, they will often go out of their way to provide useful information.
I learned early on in this process that it can be tough–on the writer, that is. It’s uncomfortable enough describing a fictional crime to a real detective (especially if you happen to be sitting in an interview room at the time), but even more so when your imagined police response, garnered from years of watching movies/TV shows and reading detective novels, is, politely, declared to be unrealistic. For several moments after learning one of my plot points was not at all feasible, all I could think was that my previous weeks of work had all been wasted because the realistic response would take my story in a completely different direction. But as my conversation with the detective continued I ended up not only with a solution to that particular arc of the story, but also several more potential plot points which I had never considered.
The experience taught me that there can be quite a difference between what you know and what you think you know. And while fiction allows for creative license, to wander too far from reality in contemporary novels is likely to turn off those readers who do know the subject. So maybe that advice for fiction writers should be amended to "write what you know you know" — not what you think you know!