Two years after a launch accident (er, "unscheduled disassembly") at Wallops VA, the return to flight is finally here. There is an ISS resupply launch tonight just after dark at 8:03 PM EDT. Weather at the moment looks good. Should be visible for much of the mid-atlantic US east coast. More info
here, and there should be various live streams of the launch online.
Look to the SE. It will be at low elevation, so look for a spot with a low horizon. A fist held at arm's length subtends about 10 degrees. Depending on your location, it should be visible about 30s after launch.
Use this
OA-5_Viewing.kmz file in Google Earth to simulate the view from your location.
Here is an example for a ball field in Bethesda, MD:
And Boston Common:
Here's a
composite of several 20s exposures of a Wallops launch as seen from north of Baltimore in 2013. Ken has a really nice photo of this launch from D.C. The actual rocket plume will look like a bright, possibly flickering, moving dot. You might also be able to see the first stage burnout and coast, followed by the second stage ignition.