Note: I've had both internet access issues and an exceptionally busy couple weeks in my personal life, so posting has gotten a bit sporadic of late. Hopefully this week will see both of those things resolved, but sometimes there are more important things than blogging, so don't be sad if I miss a day here and there, I still love you just as much.
There are a lot of differing opinions within the transportation cycling community (including whether the fact that we all ride our bikes to get places means we're a "community," after all, you don't talk about the "pedestrian community" or the "light-rail community" or at least nobody I know does), but pretty much everyone can agree that being hit by cars kind of sucks.
It's become something of a cliche that no matter what bad behavior he or she is indulging in, a driver who hits a cyclist will always exclaim "I didn't see him!" or "she just came out of nowhere!" This is usually some version of the truth, if the driver had seen the cyclist, he or she probably wouldn't have it them, but "not seeing" is often a result of "not paying attention." There isn't much we can do about distracted drivers, but we can stack the odds in our favor by making ourselves easier to notice.
This doesn't necessarily mean dressing head-to-toe in neon-colored reflective gear,and festooning your ride with a dozen flashing lights (although if that's the way you want to go, who am I to say you're wrong) but using head-and-taillights even when it's not fully dark, and putting a bit of thought into your clothing choices in conditions with poorer visibility certainly can't hurt.
I normally just ride around in my street clothes, for example, with little regard for whether they contrast with the background. However, I usually have a hi-viz vest, of the type used by construction workers, stashed in my saddlebag, and when it gets rainy or foggy, I'll wear it or lash it to my saddlebag. I also look for raingear in bright colors, again, to make myself more noticeable. If I know I'll be out and about around dusk I'll often opt for a lighter colored shirt, although I rely more on my lights and reflectors to make myself stand out.
Lighting is important, of course, and I favor a flashing red taillight, or possibly a combination of one flashing and one steady taillight. I have a front headlight that's bright enough to navigate by, and which is visible from quite a long way off.
One more thing that affects your visibility is your road position. Riding on the sidewalk makes you invisible, riding against traffic makes your speed and position harder to judge, and riding too close to parked cars makes you less noticeable. Ideally you like to be far enough into the lane that you have a bit of empty asphalt around you (conditions and traffic permitting, of course) so you're not blending in with all the roadside clutter. By going from an "object on the side of the road" to an "object IN the road" you're forcing drivers to pay attention to you.
Sometimes this will mean pulling out all the way into the lane and making drivers wait until the roadway widens enough for them to pass safely, which can be a bit nerve-wracking at first, and can annoy the less considerate types of motorists, but I say if a driver is annoyed with you because you're in their way, that means that they KNOW YOU'RE THERE!" After all, they don't WANT to hit you, so if they see you, drivers will usually give you the space you need.