I have a good friend who’s moving to Washington, D.C. and trading her car in for a bike (yay!). She came to me for some advice. Here’s my best attempt to be concise on the subject:
Buying a bike:
Until you know more about bikes, there will definitely be some peace of mind in buying new over used (though buying used from a bike shop would be a different story). Visit a local bike shop (or multiple local bike shops). Tell them where/how you plan to ride the bike, and see what they suggest. Dress so that you can actually test ride the bikes. If they try to put you on a fixed-gear bike (AKA “fixie” or single speed), don’t buy it, unless you plan to only bike in an area with ZERO hills.
As far as the cost, you may have considered this, but you’ll be saving a ton of money by not having a car. There are a variety of calculators, and different factors based on location, car model, etc., but owning a car can end up costing around $6000 a year once you add in insurance, registration, maintenance, car payments, parking fees, and gas. And that’s every year, not a one time fee. I understand your hesitation, and definitely went through it myself, but $400 is a small fraction of what we pay (often unquestioningly) for our cars.
If you want to bike to work in your work clothes, consider a bike with a drop bar. Also, it sounds like you’ve already started thinking about accessories. For commuting, I would definitely recommend fenders. Even if you don’t ride when it’s raining, you will ride on wet streets — streets that will splash up all kinds of lovely stuff onto you. Ask whether the bikes you’re looking at have clearance for fenders. We really like our Planet Bike fenders, they’re plastic, which means less rattling than metal, and they seem very durable. If you buy the bike and fenders at the same shop, get them to install the fenders for no charge.
A few basic pointers:
Look for local bicycling organizations in your area, and take a bicycle education course if you can find one. Sure, this is something you learned how to do when you were a kid, but the class will make you a more confident and competent cyclist.
Here is the website where you can take what is basically the classroom portion of Traffic Skills 101 online: http://www.bikeed.org/. Definitely not a replacement for actually riding with someone who knows his/her stuff, but somewhere to start until you can attend an in-person class — and it’s free!
Make sure you’re as visible as possible — don’t ride right up against the curb, especially at intersections, b/c most drivers won’t be looking for a moving vehicle at that point. When you’re riding next to parked cars, make sure you’re out of the “door zone,” i.e., the space where a car door would swing out if opened. This is actually a huge danger for bikes and can cause really serious accidents.
In cases of narrow lanes (and fairly low speed limit streets, lets say < 30mph), the safest place to ride is often the middle of the right-most lane that serves your destination, this is called “taking (or controlling) the lane.” It’s important because it avoids giving automobile drivers the false impression that there is actually room in the lane to pass you safely, when that may not be the case in narrow lanes. The whole “where to ride” on the road thing will get easier with practice and after taking one of the classes. After the class, you’ll wish that EVERYBODY (drivers and other bikers) had to take the class before going out on the road with their vehicles.
If you have any specific questions about cycling, please leave a comment and I’ll get back to you with an answer. Happy riding!
Her Green Life 
Great title! I don’t know if I’d be brave enough to do much riding on streets with any serious level of traffic. I’m so thankful that Denver has such a wonderful system of bike trails.
I was at a festival this weekend and there was a company there showing off their cool electric bicycles. They’re basically like a normal bicycle, but they have an electric motor that you can kick on to help you get up the hills. I suppose it sort of defeats the purpose of biking in some ways, but if I was going to try to commute on a daily basis in a place with serious hills, and needed to arrive looking semi-descent (as opposed to covered head to toe in sweat) I might seriously consider it. They let me try it out on a fairly steep hill and I must say it was quite a treat! The groovy factor was very high, but then again, so was the price tag (in the neighborhood of $2k). Anyhow, here’s their website if you’re curious: http://www.smallplanetevehicles.com
I don’t know much about electric bikes, but they are potentially a good option for all the reasons you mention. In general, if it gets more people riding bikes, it’s worth a try. Copenhagen, held up as a paragon of bicycling, is flat, but many places don’t have that advantage, and hills can be a pretty big barrier for some people. The price tag does limit the audience, though.