The Platte around Casper has some very good fishing. The area near Government Bridge west of town, Lusby, and the stretch below Alcova Dam are all good and have public access. Another access point is just west of the "narrows", west of Casper. I have never fished it, but the area around the power plant near Glenrock is supposed to be good, and there have been habitat improvements on the river near Douglas. So, the short answer to your question is "Bring your fly rod!". Have fun.