Of prime importance on any tour is safety. There are some cyclists - self-proclaimed adventure cyclists - who relish rehashing tales of near-death experiences and immense suffering on the trail. We've all read the stories in various travel magazines. Instead, how about some common sense preparation to make way for a really fun tour?
Three key items must be on your packing list; a first aid kit, all required prescriptions, and medical insurance cards (more about that under Necessities). Thankfully, during my trips, the only thing I've had to use was the first aid kit. Beyond that, a few other items will greatly improve the ride. For some of us, a bike tour may be the first time riding in the saddle for hours on end. Day two with saddle sores is a rough way to start the morning. Buy some Chamois/Anti-Chafe cream, try it out, and bring it along. Don't forget sunscreen and insect repellant, and write down a list of all your emergency contacts. Yes, I'm aware it's all in your phone. But phones go missing.
We want cars to see us. We really, really, want that. Make sure your bike has front, rear, and wheel reflectors. It's actually the law in most states. In fact, some (or most) states dictate that pedals must have reflectors - and may be illegal to sell a bike equipped with pedals that don't. Remember those cheap clunky platform pedals with orange safety strips that you quickly replaced with cool SPD-style pedals? That is if your new bike even came with pedals. Most higher-end pedals rarely leave room for reflectors. Wearing a pair of ankle reflector strips can help.
Mount a front and rear light. Make sure that reflectors and lights aren't obscured by your packed bags. Most racks and bags have mount points to install reflectors. Check what type of batteries you need and pack spares (I include this under Necessities). If I'm biking on a busy road with a narrow shoulder, I'll attach a large reflective triangle sign to my rear panniers. It's all about visibility. That's why I favor my bright yellow panniers. Install a bike bell - it's great for riding on trails shared by cyclists and pedestrians, and if you happen to be traveling in many European countries, it's required.
And this last tip is a doozy - don't cycle when it's dark and/or rainy. I know that's how many days end, but that's where planning becomes so critical. No one wants an accident to cut their tour short.
Adventure Cycling has a few suggestions for Safety Tips for Bicycle Touring