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
DCR:
161.040 (primary channel)
160.935 (switching channel
MDDE:
160.695
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.