A radio scanner is a must-have piece of equipment while railfanning in Delaware (unless you are on the Amtrak line, then use the Amtrak 'Track a Train' website or the Intercity Rail Map website)
Here are some of the main frequencies that should help you catch a couple of trains
A live radio feed is usually up on the Redden railcam, hosted by Delmarva Railfan Productions on youtube. It hears the majority of traffic the originates in or passes through Harrington.
DCR:
161.040 (primary channel)
160.935 (switching channel
CSX:
160.230 (Ex- Chessie lines - Road Channel)
161.100 (Philly sub ispatch)
NS:
160.800 (NS dispatch)
160.860 (Edgemoor yard)
160.890 (Chrysler yard)
General Convenience:
452.9375 (head of train device)
457.9375 (end of train device)
These help to know if a train is around. This channel will squawk if in range of a train, generally only a couple of miles.