I would say that in relatively clear, relatively low water, a floating line should be fine. When the water gets deep and murky, you may want a sinking tip to get the flies down deep. This naked advice really only scratches the surface though. I would tell you that I only ever fish a floating line in rivers, just because I like it better. Finding what you like is where the real answers lie. And you'll only know what you like by trying stuff out (and, God willing, catching the fish).
In most big rivers, fishing for big-game from the bank is extremely difficult (IMO), especially with flies. That said, many people are very, very good at it. Really it comes down to recognizing the water where steelhead hang out. I usually try to find a good trough, and then I fish the top thoroughly; really try to get a fly through the entire top, without scaring fish (stay high, and land your casts well above the real beginning of the trough). then I move relatively quickly through the body of the trough, because that is where you are least likely to find fish. Then when you get close to the bottom, stay high, and work the bottom of the trough, hard. There ARE fish in the bottom of the trough, the key is ticking them off with well presented flies. For the record, when I say top, I mean up river, and the bottom is the downriver portion; I am not referring to depth.
As far as what flies to use, I would say go to your local fly-shop, and humble yourself to the owner or employee. A new fly fisherman is a potential gold-mine to a store-owner, and if they make you feel like a noob, or don't give you advice freely, go to the next store. Ask them what flies they are using, how deep they are fishing them, what type of line they are using, etc...
Good luck,
Ev