I’ve done a fair bit of bicycle commuting over the last 10 or 12 years, and have developed a few rules that by now are strongly ingrained. I don’t think about them often: they’re just part of how I ride. Still, it’s beneficial to write them down.

A few things about these rules:

• This list is not all-inclusive. There are almost certainly things that I forgot.
• Although I’ve called these “Rules of Bicycle Commuting,” most of my rules apply to road bicycling in general.
• A rule’s position in the list does not necessarily reflect its importance.

Rules of Bicycle Commuting

1. You forgot something. Seriously. I’ve commuted to work hundreds of times, and I often forget things. I’ve forgotten my water bottle, my office key, my wallet, and I can’t remember what all else. How I managed to ride a mile before I realized that I forget my helmet is beyond me. But I did it. If you’re prone to forgetting things, make yourself a checklist of the important stuff, and use it. Works for me.
2. Wear a helmet. It’s the law in some places, but it’s really a matter of common sense. I’ve laid the bike down countless times (mostly when mountain biking), and it’s never been because a car hit or almost hit me. Yes, the helmet can be hot and can give you “helmet hair.” Deal with it. Your head is irreplaceable.
3. Remember the Law of Tonnage. The Law of Gross Tonnage is a nautical convention: the smaller vessel must yield the right of way to a larger vessel. It’s common sense, based entirely on physics: the smaller vessel is more maneuverable, whereas the larger vessel might not be capable of getting out of the way. My modification, applied to bicycles is also common sense: Never argue with somebody whose vehicle out-masses your own because you will lose.
4. It doesn’t matter who’s right. Related to the previous rule: When in doubt, yield the right of way to cars. You may be “right” in assuming that you have the right of way, but that’s small consolation when you’re road pizza.
5. Wave with all five fingers. Most drivers are curteous and will give you space. Others will honk, yell, scream, curse, or otherwise try to make your life difficult. You may be tempted to give them the one-finger salute. Resist the temptation. Ignore them, or smile and wave with all five fingers. Doing otherwise risks putting you in a position where the Law of Tonnage can be used against you. Result, again: road pizza.
6. You’re invisible. Drivers often don’t see bicyclists. Drivers should be observant, but it’s in your best interest to make yourself as visible as possible. Never assume that a driver sees you. When you’re lying on the road with a broken leg or worse, the matter of whose fault it was is pretty minor.
7. Lights. If you’re going to ride at night or even close to dawn or dusk, get a tail light that blinks and a head light that you can mount to your handlebars. Those are so others can see you. Side reflectors are also good. If you want to see reliably, get a helmet-mounted light so you can direct the beam around corners and also at drivers so you know that they see you.
8. Make your intentions known. Most people use their turn signals when driving a car, and of course your brake lights work automatically. Your bike doesn’t have those luxuries, so you have to make do with hand signals. It’s best if you point to where you’re going. Forget that silliness of left arm up to signal a right turn: use your right arm and point to where you’re going. And if you’re stopping, don’t just hold your hand down with palm open: pump your hand like you’re pushing back.
9. How to Not Get Hit by Cars. Read, memorize, apply. ‘Nuff said.
10. Watch for cars entering the road. I’ve never been hit by a car. I have come close quite a few times, though, and most of those were entering the road from the right. You’re riding on the shoulder, and people entering the road often look down the road for other cars and ignore the shoulder. They’ll turn right in front of you or right into you. Make sure you’re seen, and be especially observant to driveways and cross streets.
11. Shortcuts are dangerous. Be careful when you take advantage of cutting through a parking lot. You’re not the only one who treats an empty parking lot as a no-rule zone. Keep a sharp lookout for cars that are cutting through the parking lot, too.
12. Choose your route carefully. The fastest route by car may not be the fastest route by bicycle. Whereas it makes sense to take major roads with higher speed limits when you’re in a car, that 25 MPH residential street is shorter, and faster, on your bike. Besides, it keeps you off the busy streets and reduces your chance of getting hit. When in doubt, take the safer route, even if it’s a bit longer.
13. Carry a spare tube and know how to change it. City streets are hell on bicycle tires. There are nails, screws, glass, shredded soda cans, construction staples, and all manner of other things that can puncture your tire and cause a flat. A spare tube will save you most of the time. If you don’t know how to fix a flat, go to your local bicycle shop and ask for a demonstration. Then go home and practice until you can do it reliably. With practice, you can do it in under five minutes. You might also consider carrying a piece of Tyvek (cut up an old FedEx envelope) or some similar material to put inside the tire in case the tire gets more than just a little puncture.
14. Get puncture-resistant tires. I used to get a flat at least once a week. One memorable day I got three flats on the way to the office and another on the way home. Then I discovered puncture-resistant tires that have a Kevlar strip in them. Now I get flats … almost never. I went an entire year (more than 3,000 miles) without a flat. I ride on Specialized Armadillo tires, but other manufacturers have similar products. Puncture-resistant tires are heavier than racing tires, but in my opinion the tradeoff is worthwhile. I seriously dislike having to fix a flat.  Oh, and don’t waste your money on thicker “puncture-resistant” tubes.  My experience is that they provide no benefit.
15. Learn to do simple repairs. A bicycle is an incredibly simple and reliable machine. Still, things break from time to time. Most good bike shops offer basic maintenance classes where you can learn to fix a flat, perform simple adjustments on your brake and shifter cables, spot-true a wheel, and a few other things. Learning how to do those things can save you from an uncomfortably long walk.