Welcome to PAFF, lots of great advice given thus far.
I'll second the Nagy book, it is loaded with tons of valuable information. When I go to Erie, this book comes with me.
When the steelhead start showing up in Erie, so do the crowds--even during the week. There are pretty much always going to be people there fishing for Steel but if you stay away from the mouths and take a walk from an access point, you can find open water.
Another important aspect to keep in mind is posted water and access. Be respectful of the landowners and take out what you take in. Between garbage, foul language and behavior it seems more and more land is posted year after year.
Weather is a huge factor. Like Alby said, the transition after chocolate brown to slightly stained is when I've had my most productive trips. I have found that having flexibility to just go is best at least for me, whereas planning weeks or months in advance can be hit or miss due to weather/stream flows.
To cut down on the learning curve, you might want to head "up-er" with some guys from the area, there are lots of us here that make the Erie trek. The Steelhead Jam would also be a good way to learn new water and fish amongst good company.