The internet is a wonderful thing (most of the time). For the angler, there is a wealth of information about when, where, and how to catch more fish. And lots of it is true and much of it is helpful. I want to concentrate a bit on the where part of the equation.
Anglers - at least those that have been around the block a few times - know better than to put too much on the internet. That said, there is a ton of information out there that can help you find fishing spots. This will be pretty Wisconsin-centric but the ideas apply everywhere, the resources will be different depending upon what information your state (or country's) resource agencies put online.
Fishing Regulations
Your state's fishing regulations provide a lot of information about not only the regulations (well, duh...) but also about quality fishing locations. That lake with the 50 inch Muskellunge limit probably has some big fish in it. The stream with special regulations may - or may not - be a place that is well worth fishing. The regulations are not the end all, be all of finding places but you need to know the regulations and there is some useful information in the free regulation books. While they are online, I like having paper copies in my boat and vehicle. Pick them up for free where you can purchase licenses or at your nearest DNR service center.
Fishing Reports
While there aren't always a ton of fishing reports online, there are some and even the dated ones can be useful. The habitat conditions, hatches, and effects of weather tend to stay fairly similar over time. Thus, searching for fishing reports - even if they're not current - maybe be a useful way to find more information about fishing. The best source of information may be your local fly shop. For us in the Heart of the Driftless, the reports from the Driftless Angler are a great up-to-date resource. Your local fly shop is likely to have reports online and/or on their Facebook pages.
Online Maps
Probably the best way to really figure out where to fish is provided by a number of online maps. It is the best way to have an idea what the are will look like before you go there. Some of the online maps that the DNR hosts also provide other important information such as easements, public lands, boat launches, fishing regulations, and other useful information. As mentioned above, the trout fishing regulations booklet is a great tool as it. These online GIS (Geographic Information Systems) are a wonderful resource for hunters, anglers, and other people that want to spent time outdoors. You can get "lost" for hours online looking up and down rivers for access points, pools, rapids, and other features.
Google Maps is probably the best known and most used online mapping service, largely because it is easy to use and the imagery is up-to-date for most of the US. However the probably the best and most helpful mapping resource for the trout angler is the Wisconsin DNR Trout Regulations and Opportunities Users Tool (T.R.O.U.T.). What is great about his resource it is really (nearly) one stop "shopping" for the trout angler. Easements and public lands are georeferenced so you can be sure that you are accessing streams legally. Additionally, there is information about habitat improvements and fishing regulations. There is two small drawbacks to the site. First, not all the county easements are on the site. Second, the zoom feature with aerial photographs does not have the resolution of Google Maps so I often use TROUT and then find the location in Google Maps if I want aerial images that all you to zoom at a scale where you can see stream features better.
Many counties have their own easement programs which are often not found on other online sources. The Wisconsin Sea Grant has a list of County GIS sources that is a very useful place to start your search. Additionally, a quick online search of the county name (you might want to add "WI" or "Wisconsin" to the search) and GIS or land information system will probably provide what you are looking for.
Other sources you might find useful are the Chequamegon - Nicolet National Forest website, Wisconsin State Parks, Wisconsin State Forests, County Forests, Managed Forest Lands (private lands *often* open for some public access, Lower Wisconsin Riverway, and Wisconsin County Parks. Travel Wisconsin is a great resource for finding all sorts of things to do, places to eat, and events.
Paddling Resources
Resources for paddlers - canoeist, kayakers, and rafters - are probably one of the most useful and overlooked resources by anglers. Many of these resources will provide access points; general information about the stream, river or lake; and information about unique features like rapids and rock gardens that might be useful to the angler. Most of the state's better known and more popular paddling rivers will have no shortage of information online.
My personal favorite is Miles Paddled, which also has a Facebook, Twitter, and YouTube presence on the web. They have paddled waters ranging from many of the state's popular trout streams to large rivers like the Mississippi and Wisconsin Rivers and most everything in-between. The detailed trip reports along with some very good photography make the page a great way to see what a stream looks like before you fish it. Wisconsin River Trips is another very useful site.
Additionally, Wisconsin is home to some very popular paddling rivers that often have useful resources that highlight access, public lands, and the how to best get through some of the state's best whitewater. Mike Svob has two books on paddling the state that are great resources for maps and information (see below). There is not enough room to list all the sources for paddlers and campers in the state but in the past, I've found the St. Croix National Scenic Riverway, Paddle the Flambeau River, Wisconsin Wild Rivers, and Wolf River Wild and Scenic River sites to be useful (among plenty of others).
Book - Paddling Southern Wisconsin
Book - Paddling Northern Wisconsin
Weather and Streamflow
Nothing can ruin a fishing trip more quickly than bad weather and high and muddy streams. Fortunately there are tons of great resources for weather and the United States Geological Survey maintains a number of streamflow gaging stations. These gaging stations, at a minimum, record the gage height (surface level) but also may include other data, including temperature which can be very important. These stations and more information are available through their WaterWatch website. For Wisconsin, real-time data are available and if you "play around" on the website a little bit, you'll find ways to see past data and compare current stream flows to historic stream flows. Additionally, some of the paddling resources are great resources to understand what
I use my phone for weather applications (I like AccuWeather and My Radar apps) but I have not found an app that I love for streamflows but the USGS webside loads on your phone pretty well in my experiences. I also find the Wisconsin State Climatology Office website a good resource and their Wisconsin Climate Watch a valuable resource, particularly to visualize recent (24 hour and 7 day) precipitation totals and departures from the average.
Trout Stamp Expenditures
If you got this far, you deserve a really awesome tip for finding great places to fish - and it is FREE. Wisconsin is a bit unique in that our inland trout stamp is not used to pay for stocking fish as it is in many states.
Wisconsin State Statue 29.2285 (1)(e) states: “The Department shall expend the receipts from the sale under this subsection of inland waters trout stamps on improving and maintaining trout habitat in inland trout waters, conducting trout surveys in inland trout waters and administering this subsection.”
So, if you have not explored the Expenditures of Inland Trout Stamp Revenues, it is a great resource to see where your trout stamp purchase goes and a great resource to find where habitat improvement projects and maintenance have occurred.
What fly do I use?
For many fly anglers, it is about the bugs. There are tons of hatch charts and a few databases online that are good resources to see when and where different "bugs" are likely to be hatching. It is, of course, all weather and stream temperature dependent but they will generally give you pretty good idea of what to expect when. See the resources below for a number of links.
As for what fly to use, well, that's often a matter of choice and experience. We all have our favorites and often times confidence in them is as important as anything. I doubt fishes generally are all that selective to John Bethke's Pink Squirrel or Mat Wagner's Coulee Scud. Call your local fly shop, ask some friends, or make a post on a message board or Facebook page and folks are generally MUCH more willing to tell you about flies than they are fishing spots.
To Wrap it up...
It has never been easier to find fishing spots, for better or worse. The internet is a wealth of information but it takes a little time and effort but much of what you need to know is there. Don't expect others to give up their often well earned experiences about where to fish, certainly not publicly. The search is much of the fun.
Resources
At least for Wisconsin - and I am sure it is true of most states - there are a TON of great resources. Here's a pretty good list to get you started.
Books and Online Resources:
Maps:
Online Maps - Wisconsin Trout Stream Maps (by County)
Online Map - Wisconsin TROUT Tool (WDNR)
Online Map - Wisconsin DNR Public Access Lands
Stream and Fisheries Data
Database - Wisconsin DNR Fish Stocking Database
Website - Wisconsin DNR "Find a Lake"
Website - Wisconsin DNR Fisheries Survey Reports
Website - Wisconsin DNR Fisheries Publications
County GIS Maps for the Driftless Area
Hatch Charts and Resources: