A good place to start is to figure out which part of the state you want to go. The western side of the state (from I-25 west) is the mountains. There are hundreds of high country lakes and streams that hold trout. If you backpack into a wilderness area you'll find less fished areas and easier to catch fish. Pick a national forest (San Juan, Gunnison, San Isabel, Roosevelt, etc.), order a forest map and go from there. There are some bigger rivers such as the Arkansas and Colorado which are great fishing too and closer to towns. There are a lot of smaller rivers like the Poudre, San Miguel, Uncompaghre, etc.. that are also good fishing. Most towns on the western side of the state have a flyshop and most of the time you can get a pretty accurate fishing report from them on all their area waters. Take a look at some of their websites. For the bigger rivers it would be an advantage to get a guide but on the high country stuff you don't need one to catch plenty of fish. Good luck!
