John Goerzen blogs about (how to start) cycling to work. As I'm now back in Freiburg, in which anybody not cycling will be treated as an anti-social enviromental sinner, I'm using my bike a lot more, including cycling to work, hence I'm interested. Basically, I'm fine with what John has put together, but I would like to share my own experiences.
First of all, I'm concerned with Johns reference to cycling helmets. It is not so that helmets are required for cycling. I believe that this misconception is a common reason why people in recent years have come to believe that somehow cycling is a dangerous activity in the first place, while statistics clearly say it's not (in comparison to other activities, obviously). For instance have a look at a
collection of facts around the danger of cycling. There is also some doubt about the usefulness of cycling helmets, have a look
at the results of the helmet law in Australia. Now, whether one decides to where a helmet or not is up to you, of course, but the main fact to keep in mind is that cycling is in no way particularly dangerous.
John also mentions that for safe travel a key point is visibility, to which I whole-heartedly agree. However, Johns's sentence starts with "Unless there are dedicated bicycle-only lanes or paths ..." which should be taken with a grain of salt. There are studies, which I unfortunately had more than once the chance to verify, that bycicle-only lanes add a risk of their own. First of all, more often than not, you will not be as visible as you should be, especially if the lane is behind parking cars . Next, any biker on such lanes should take good care of any interference with pedestrians and/or car traffic. Especially where such lanes cross exits of garages and houses or when cars are parked directly beside the lane, be extra careful. I generally don't like bike lanes because more often than not they're in a shape no car driver would accept, but that's not the real point: the point is that bike lanes lure you into feeling extra safe while adding in some little surprises of their own.
But there's also another point to be made wrt. visibilty: Being visible alone won't save you, i.e. you can't trust that others will always behave correctly just because you do. Instead it's a lot more important that you are aware what other traffic participants are doing instead of making them aware of what you're doing -- only the first option is an active one, the second is just passive.
Now that we've dealt with the safety issue, let's talk about the fun. How fast you're going is up to you. I find that I can't really go slow (well, at least I feel like I'm not slow and there are not too many people going faster). I like a light and fast turn, so I use a relatively low gear -- think Lance Armstrong, not Jan Ulrich. And I shift gears really often so that my pace stays more or less the same regardless whether it's going up or down. Of course, this is only possible if you have relatively many gears. Don't expect too much from yourself btw: it's okay that you feel exhausted after a seemingly small way at first. It's also okay when you don't use the bike every day right from the start -- actually it might make a lot of sense to take a break between your riding days, depending on your fitness and the amount of cycling you have to do.
Of course, going quite fast by bike means that I'm sweating -- bringing spare clothes helps. And another point: if the weather is hot (there is currently wind from Africa blowing all the way up to Germany which means it's unusually hot these days), go early in the morning when it's still relatively cool. I would also suggest taking rain clothes with you, regardless of what the weather report is saying. I use a bike bag in which I take my rain clothes, some repair stuff and an air pump. I never really unpack it, so that's simply not an issue.
Another point: try to find a nice way to ride. This might require trying several alternative routes, but if you're lucky you might find a route that is fun to go. This helps to keep the motivation up. I know what I'm talking about, since in my old job in Mannheim I didn't use my bike as much as I should have because there simply was no nice route for me to work -- I always felt a little hunted on the road. Now, in contrast here in Freiburg, I've found a route which goes besides the river Dreisam for about five kilometers which is just nice in the morning, which means that I'm far more motivated to go the 10km way here than the 3km in Mannheim.