|Nice to see this bridge without barbwire and no-tresspassing signs all over it.|
Step 1: Find the river you want to fish. This would be a river that is legally navigable and allowed for recreation. This includes most big rivers, and many small rivers, such as the Ruby. I would highlight recommend one that has fish in it as well. Don't
Step 2: If there is not a giant public parking spot (which are good to launch boats from and suck to fish at anyways) find a bridge. By state-law there is a 60' right-of-way. This means that when combined with the high-watermark of the river, you can get in and go fishing!
Step 3: Go Fishing! Keep your feet wet (below the high-water mark, wet feet is the easiest way to do this if it's a small river), don't litter, and don't trespass. Thankfully, Montana isn't some dumb-ass state like Colorado or Wyoming where you can own the bottom of the river. Public land and water in Montana can be (Gasp!) used by the public. Be thankful that we have a Supreme Court who believes in public access and public land.
Note: In no way do I condone trespassing, which would surely not help the case of the phenomenal stream access laws we have in this state. Be courteous of the landowners who are generous with access, don't litter, and don't be a cox. Also, think about where you donate those precious dollars to conservation. The juxtaposition of DU's "conservation" and willingness to bend to one donor is frustrating, and certainly makes me think about the conservation organizations I give to.