If you could only hike one section of the trail, it absolutely has to be Section 3 (19.3 miles) from Cherry Bend to Lick Branch. If you want to do a little more mileage, do Section 2 first (starting at White Rock Mtn, very cool place) for a total of 38.2 miles.
Fishing a long the OHT is hit or miss. Section 3 contains Indian Creek which is a decent sized waterway and might land you a few. Your best bet would be to go to the Mulberry River, which you must cross over (by car) to get to the trail head.
The Mulberry River is quite a well known river for floating, but has some good fishing waters as well.
Order your OHT Guide book directly from the source:
http://store.cloudland.net/merchant.ihtml?pid=2&step=4