In regards to your original question, steelhead fishing for the average bankie who doesn't immediately have good local info or access on great holes is tough and not necessarily intuitive, even if you have a lot of experience fishing rivers for bass, trout, etc....I have a couple thoughts for you:
1) OFF - there is so much information on here in previous threads it's ridiculous, put in some time searching keywords and you'll find some great posts. Collectively you can get a good idea of different techniques to use, spots to fish, and times of year. As far as what works in certain conditions, that's more something you'll have to figure out on the ground.
2) Guide - expensive, but so is wasting day after day out there, losing gear and burning gas, not catching anything. You can learn all the holes on a particular stretch of river and the appropriate techniques.
3) Go to the hot spots and watch - head out to the super-popular holes (Mills Bridge on the Wilson, mouth of Three Rivers on Nestucca, hatchery on N Fork Nehalem, hatchery area on Sandy, Meldrum bar, etc..) leave the rod behind, watch, be nice and ask a few questions, you'll at the very least learn something about how to fish those holes.
4) Water levels are really important for steelhead/salmon, keep that in mind because it's related to everything else you'll learn. One hole might only fish really well, or one technique might only work, at a specific water level. Time of day, water clarity and temperature, tides, etc. are all factors as well.
As far as the Columbia side of Sauvie Island, I'm no expert but I'd say it's far from a year round fishery..if there aren't a bunch of people plunking and boats trolling then there probably aren't any fish worth fishing for. If you're close to the Sandy & Clack head out to Meldrum Bar or the hatchery area on the Sandy to see what's what, that'll be a good start. However, as stated above, the coastal rivers are the hot spots right now for sure.
