locks: kyptonite or abus chain locks. the abus ones are a bit heavier (the company specializes in industrial locks) the chains however are identical. get a set of locking skewers if you are running quick release. they use a key, that is actually pretty specific to each set. these will prevent wheels and seats from being stolen. If you have nice components, remove or mask the logos. You can also put a bit of epoxy in any bolt heads so that it is harder to strip the bike. number one thing is to make the bike look like shit. i've seen $4000 custom ti mountain bikes that looked like pos delivery bikes at first glance.
as for riding in the city, if you are confident on your bike, i think is is safer to be on the offensive at all times. Try and stay ahead of the traffic. When you come to a one way street, you can move to the side away from approaching traffic, and look to see if the road is clear before you have to put on your breaks. If you get a good series of lights, you can usually do 4 or 5 blocks without ever having to deal with cars.
Pedestrians are dumb (no offence to pedestrians). always keep an eye on them. The worst is when they see you, get startled and stop walking, keep an eye out for this, and give yourself room to avoid it. If you're coming up to a group of pedestrians, pick your line carefully (same applies with taking right hand turns where people are crossing).
Watch for movement inside parked cars to avoid being doored, and also keep an eye on the front tires on cars that are idleing. it provides a good clue that they're about to pull out.
I ride in nyc traffic on a regular basis. I have only had one incident so far, and it was pretty small. Riding is the best way to get around in the city. I hope this stuff helps.
