- Find a light weight bike
- Add a rear rack
- Get bags/bungies
Rear racks are necessary if you ever plan on carrying anything. Yes you can just wear a bag, but a rack is extremely useful in the long run. You can use a rack to carry specially designed bike bags. Small bungies should be kept on your rack so you can carry unexpected items.
There are a variety of bag, generally called panniers, that fit on racks. One simple easy solution, that is weatherproof, is buckets with mounting brackets. These panniers can be made from old buckets, so the environmental impact is low. You can purchase these ready made, or make them yourself! If you'd prefer a bag, look around for used ones. They can be hard to find, but the price savings are amazing, not to mention the minimization of the environmental impact!
Lights are a necessity. I don't care if you think you're only going to be riding in daylight, you need to get them! You'd be amazed how early, and quickly, it becomes dark in the fall. Lights also provide a measure of safety on rainy days, when it's harder for people to see.
Try to find lights that use AA batteries, since they're easy and cheap to replace. I run my headlight off of rechargeable AAs. You should try to carry extra batteries with you. In Oregon, you are required to have a white light on the front of your bike if you're out in the dark. This allows cross traffic to see you more easily at intersections. You should also have red lights for the rear of your bike. I would not want to ride without these, since it makes me feel safer knowing that drivers behind me can see me. I have a great red light that is attached to me helmet. This way I always have a light with me, so I'm prepared for unexpected lighting changes.
You don't really need specialized clothing for biking. You do need a helmet. Purchase one at a bike shop where they will fit it for you. Wear your helmet every time you bike! They're light weight and fairly inexpensive. $30-35 is a small amount to pay for something that can save your life. You don't look stupid with one on. It's the people who don't wear them that are showing their stupidity.
If you live in the NW you will want rain gear. I quickly learned that jeans are the last thing you want to wear in the rain. I bought a set with a simple yellow rain jacket and pants at the local army surplus store. I quick trip to the local bike co-op and I had reflective tape to apply to my rain gear. For under $25, I have gear that keeps me dry and visible.
If you're in the Portland Metro regions here are some helpful links:
byCycle provides bike route planning. I use this site all of the time to plan various trips.
City Bikes one of the local bike co-ops. Sells the buckets pictured above.