You didn’t say what part of the Pacific NW you would be fishing. There are many steelhead rivers from northern California up through Washington and into British Columbia. And, each river can be quite different than the next one up or down the coast. Even the locals sometimes have a tough time deciding which one to hit. Hopefully your friend is on top of things and can get you into some fishies.
The big issue, this time of year, is the weather. Once the winter storms start coming in, most of the rivers run much higher and usually muddy. That makes them mostly unfishable, even with lures or bait. When a river is running high and muddy, forget about flies.
The best fly fishing for steelhead is for the summer run fish, in lower and clearer water. However, you can sometimes get lucky and hit a river several days after the last storm, when it is dropping and clearing…and the fish are both more accessible and can see your fly better.
When it comes to flies, lines, presentations, etc., that is where there are local diffeerences too. If you are fishing summer fish in small streams, with low clear water, you can get by with a six weight outfit and long leaders with small dark pattern flies. In the big raging rivers you need at least an 8 weight setup with fast sinking lines and short level leaders. A lot of winter fly flingers opt for cannonball shooting heads.
Most areas have favorite fly patterns, but there are lots of flies that will work on most streams. In high, cold “colored” water, you need to fish big bright stuff to get the fishes’ attention. Almost any pattern with hot red, pink, orange or chartreuse will work at times. Blacks and purples are good too. HERE IS A LINK to a website with some patterns to look at. If you go to your favorite search engine and enter “steelhead flies” you will find a lot more to look at, along with more good info on fishing them.
You can also research the areas or the rivers you plan to fish. It is amazing how much good stuff you can find online if you spend some time looking for it.
One other note. When the rivers are too high for fishing flies, you can sometimes dredge a few fish out of the quieter holes and runs by casting big spinners or spoons. However, since most steelhead rivers are snaggy, you can leave a lot of “bling” on the bottom without anything to show for it.
Good luck. Even if you do not catch a single steelhead (or any married ones) a trip to that area is always a spiritual experience.