Crash -- by any chance are you riding the Capital Crescent Trail? If so, you'll want a decent light since much of the trail is very dark and there will be other riders, pedestrians and deer just to make life interesting. One or two rear lights are also a good idea since it is easy to have people close on you quickly in the dark. I would add some reflectors at least to the front wheel or rim for any road crossings you have to make. You want to make sure you are obvious to drivers.
As for locking I think others have already pointed you to the right info. A good U-lock is essential. Combine it with a stout cable to secure wheels and saddle. Or use a second different type of lock to make your bike too much of a hassle to steal. Chances are if you are locking it up in a parking garage, you will have slightly fewer security concerns since it will not be out on the street in plain sight.
Hope that helps. If you want any info on DC area commuting (especially Silver Spring) let me know and I'll try to help.