Well, I wrote a long response last night, and when I hit post discovered my internet connection had crapped out and refused to come back.... unfortunately I don't have time to repeat it tonight. :'(
Couple of things though:
1. If you can find a copy of Trains September 2002 edition, it had a trackside guide to Cincinnati included as a supplement.
2. The McDonald's in Hamilton is a good place to have lunch and see trains; the CSX Toledo sub and the NS New Castle district share tracks through Hamilton. All northbound traffic uses the CSX tracks; southbound the NS tracks. The interchange is at Butler Street, behind the McDonald's.
3. CSX Queensgate Yard and the NS Gest Yard are side-by-side just west of Cincinnati and parallel I-75. This is a HUGE yard complex. Don't miss Union Terminal if you go there.
4. The CSX bridge to Convington KY is right next to the I-71/I-75 bridge downtown. The NS bridge is further west.
Enjoy
Tim