Eldorado Canyon State Park ranger Craig Preston has published a pamphlet describing both fly- and baited-hook fishing in the park. It's available at the visitor center. Anyone older than 16 needs a Colorado fishing license, which you can obtain at local sporting-goods stores. See www.wildlife.state.co.us/fishing for more information.
Kinsley Outfitters (2070 Broadway. 303/442-6204 or 800/442-7420. www.kinsleyoutfitters.com) provides Orvis-endorsed guides for the world-class waters of the Colorado and South Platte rivers. You can arrange a personalized half- or full-day guided fishing trip that includes transportation, lunch, and Orvis equipment. Your fishing license will cost extra.
Rocky Mountain Anglers (1904 Arapahoe Ave. 303/447-2400. www.rockymtanglers.com) can sell you a few flies or set up a guided tour. The guides have access to private ranches and know where to find secluded fishing holes on public lands. Fees include transportation, gear, and lunch.