Help, My Bike Has Gears!

One thing you should work on is getting in the habit of downshifting (shifting into a easier-to-push gear) as you're stopping. It'll make it easier to get going again, and doing it after you've stopped is a pain.

The best bike gear is one which lets you pedal at a comfortable speed, not spinning your pedals really fast, nor pushing against massive resistance. You should get comfortable changing gears regularly, and will begin to feel when you're in the wrong gear. Generally you'll want to change the rear gears more often, keeping the front gear in 2 or 3 unless you need to climb a steep hill. When changing gears remember that you need to function as the clutch: only try to shift gears when you're not putting much force through the pedals. If the gear system isn't set up properly the chain might come off if you're in too high or low a rear gear; depending on the design of the gear system it should be possible to adjust the limits to prevent this from happening. Also, if your are in a certain combination of front and rear gear, the chain can run at an angle relative to the bike, causing rubbing and a clacking noise. If this occurs try shifting the front and rear gears to align the chain better. As for maintenance - see this incredibly useful PDF (which also explains how to adjust the gear limits to stop the chain slipping off): http://www.londoncyclist.co.uk/wp-content/uploads/2010/01/Bicycle-maintenance-made-ridiculously-easy.pdf

The cadence stuff is mostly about saving your knees. Faster pedaling, but less force required. Ideally you don't want to have to really push that hard to pedal -- so you shift to an easier-to-pedal gear ratio when the going gets tougher and to a harder-to-pedal gear ratio when it's easier. http://sheldonbrown.com/beginners/index.html are a good place to start, and should have answers for a lot of your questions about things like braking technique. As for the saddle and tires -- unless you're uncomfortable, no reason not to keep them. Look into proper adjustment for the saddle in particular (it may take some tweaking before you're really happy with it, and this can change over time and even based on what shoes you're wearing!)

I'm inclined to disagree with Think_Long about breaking, if you're on a bike with excellent brakes and thick grippy tires using just the front breaks when going fast will almost always flip you over the handlebars. Best to use a combination of both when you need to stop quickly, and adjust the pressure in your hands to compensate for changes in the balance of the bike

Welcome to biking in Chicago! I think most of what you've asked has been covered, but I'll add that once you start riding regularly you might want to pay attention to the lights and your speed. That is, nobody likes stopping at lights but you can time your pace to allow yourself not to hit most lights. This falls in with the excellent advice of learning to downshift to an "easier" gear before you get to a light/stop. If you start off from a stop in a hard gear your knees will hate you. A few Chicago resources you might find interesting: http://www.thechainlink.org is the bike community's message board. Ask for advice, make friends or find a group/ride you want to join. I started going on rides through a few different groups and have made a whole new group of friends who are passionate about biking. We have a women-only http://chicagocriticalmass.org named https://www.facebook.com/CriticalLass. Rides are once a month and change location, usually stopping somewhere for a beer/dinner at the end. Dottie from http://letsgorideabike.com has a lot of posts and videos about bike commuting in Chicago, what to wear in the winter, etc. She also often organizes a "Women Who Bike Brunch" once a month which are great events to meet awesome women and get advice (like on what are good routes, for example). In the summer we have picnics, which are more lightly attended but easier to make friends at. West Town Bikes has open shops where you can come in and work on your bike alongside instructors, http://westtownbikes.org/node/185045. You mentioned riding on well maintained trails back in California. We have those! Have you ridden on thehttp://www.activetrans.org/lakefronttrailconditions yet? It's gorgeous and much less busy on week days and South of 35th. The http://www.bikingillinois.com/nbranch.html starts around Devon and goes through forest preserve (deer, nature, fresh air!) all the way up to the Botanical Gardens. It's a beautiful ride. Then there's the http://www.traillink.com/trail/green-bay-trail.aspx?gce=201304_1&utm_expid=5284793-5 that runs along the North Shore closer to the lake. You can pick up the http://www.traillink.com/trail/north-shore-channel-trail.aspx and head back to the city alongside a sculpture park in Skokie. This doesn't help with your commuting but there are options for getting out there and (mostly) away from traffic. Lastly, my favorite bike-themed event of the year is coming up July 13th. http://www.newbelgium.com/events/tour-de-fat.aspx is a free one day festival put on by New Belgium in Palmer Square. It's super fun, and there's a slow bike parade in the morning which most people dress up for.

I remember from my childhood days that using just the front brake is a good way to flip over the handlebars. Should I use both brakes all the time? Should I mostly use the back brake? How do I brake quickly to avoid any hazards? The front brake has the most mechanical advantage (engineers can feel free to correct me), so your stopping power is way better than just the rear brake. The reason people flip over the handlebars is in emergency-stop situations and they don't have their arms braced against the handlebars. If you brace your arms correctly, you won't flip. I always use front brake for stopping, the rear for slowing, and both for OMG stop nows.

One little tidbit in your "upgrades" category: if you plan to carry groceries or other stuff, the http://www.tamiasoutside.com/2009/04/13/pletscher/ is your friend. So sturdy. So much less cussing :] Yes, you'll need to buy a pump, because you want to make sure your tires are aired up before each ride. Properly inflated tires give a smoother ride and make it easier to pedal. The maximum PSI should be molded or stamped on the tire itself. Gears: when you feel like you are grinding your knees, pick an easier gear. I mostly ride a singlespeed in a not-totally-flat area, so I feel like in Chicago you probably won't need most of your gears. Just keep in mind there's no prize for it being hard to pedal. Saddle: if you like yours, keep it; if you don't, start looking for a different kind.

Avoid switching to the gears that are on opposite ends of the chain ring at the same time (ie. biggest front chainring and smallest rear chainring). The resulting angle of the chain makes it more susceptible to the chain coming off. If the chain does come off you can often re-rail it in motion by changing to the middle gears of the chainring. Just like a car low gears easier for starting off and going up hills. Cycling in high or difficult gears builds leg muscle but can also be very hard on your knees. Chicago is pretty flat though so you don't really need to worry to much about gears. Oil your chain by using chain lube and wiping it with a rag afterwards. This works the oil into the chain, removes excess that will just collect dirt and increase chain wear, and keeps it off your pant leg

Gears: This is largely a fly-by-wire/how you feel at the present time kind of thing. As you gain speed, pedaling will obviously become easier, so it makes sense to shift to a higher gear. It really just depends on how fast you want to go and how much effort you can put into the pedals. The optimum will always change. I have a 3x6 bike, and I mostly just change the front gear - I use the middle or low position to start from a stop, and shift up as I gain speed, and try to shift back down if I need to stop. I just use the rear gear for fine-tuning. Brakes: you're right that you'll go over the handlebars if you front brake too much, but your front brakes are the most effective at actually stopping you, so you will want to use them, especially if you're coming to a complete stop. You'll also want to use the rear, obviously, but you may be able to get away with just using the rear if you're only slowing down a bit. Accessories: only reason to really get a fender is to prevent butt stripe, so if you've got something back there that blocks water/road sludge kicked up by the rear wheel, you should be OK.