When first pursuing a steelhead on top there are a few things to consider. Probably the first thing to consider is how far the fish must move to take a fly relative to the water temp. You can expect steelhead to be willing to come to the surface any time the water is over 50 degrees, 55-63 being optimal. Steelhead can be caught in water as cold as 43 degrees but it takes just the right circumstances. In B.C. it is very common to catch steelhead on top even with water temps in the 30's however those fish spend all their lives in water much colder than our fish down here so they have acclimated as a species to the colder water and are therefore more active at those temps. Again optimal water temps for steelhead here in the states is 55-63 and good conditions are anywhere above 50.
Water depth is water temps counterpart. Generally speaking the deeper the fish are holding the warmer it needs to be for the fish to be comfortable to rise to the surface. The more comfortable a fish is the farther it will move for a fly. Since most summer steelhead hold in pretty shallow water, 2-4 feet, as long as water temps are over 50 your in good shape. For the very few runs that might be 5 feet or deeper water temps in the mid 50's will be better. It's also important to understand where in the water column the fish are sitting. Just because a run is 8 feet deep doesn't mean the fish are at 8 feet deep. When in deep water steelhead almost always suspend. It is common for instance on the North Umpqua to fish runs that are 6 feet plus in depth but the fish are holding suspended over rock spines in 2-4 feet of water. Rarely are they deeper than 6 feet.
Another thing to consider is that runs are usually much shallower than they appear. A winter of float fishing taught me that. Even in winter I never fished deeper than 4 feet and at that depth I spent a lot of time dragging bottom. In short if you are fishing your fly 6-8 feet deep you are very likely to be fishing under the fish where they cannot see your fly. So our ideal piece of water to take a steelhead on top will be 55-63 degrees and 2-5 feet deep. As always low light conditions will allow the fish to be comfortable in shallow water, often VERY shallow water. Low light conditions can be morning, evening, overcast days, off color water or even a riffley broken surface. On the Washougal where I grew up it was very common for fish not to hold in runs at all but in bubbly pocket water. I am sure that summer steelhead hold in such places in many other rivers as well, because these locations are very difficult to see into they offer a great deal of comfort to a steelhead. Often they are just holes in an area of rapids and are only large enough to hold a single fish and are covered on a cast or two but they are always worth a shot particularly if you can get above it and just hold there for a few moments. This brings up another thing that's good to know. When taking something on the surface a steelhead rarely grabs the item in it's mouth. They raise up behind it and flare their gills so they can suck it in. However if your line is tight they will not be able to suck it in and you'll have the very common " short strike." There are many ways to prevent this the easiest I think is to keep your rod tip up at a 45 degree angle then drop it when the fish comes up. This is vitally important when fishing a short line in pockets. As casts increase with length and more slack is added it becomes less important. My first summer of steelhead fly fishing I had raised dozens of fish to a steelhead caddis but couldn't hook them. Often I would raise the same fish as many as 10 times on consecutive casts and still no hook ups. One day I casually mentioned the problem to Bill McMillan and he told me to start dropping the rod tip. The problem of "short strikes" has since gone away.
My selection of surface patterns is pretty basic and relies heavily on variations of the Muddler. The steelhead caddis is a prime example. The steelhead caddis is simply a tailless Muddler with a dubbed body and minus the squirrel tail in the wing. I have found color in surface flies to be of minimal importance. Colors of caddis I have caught fish on are black, orange, brown and green. I am sure that any color you choose to use will be equally as effective. Also the color is determined simply by the body color everything else is natural in color. Light wire hooks make the fly skate a little better and aid in penetration but are not necessary. Size 4,6, and 8 are ideal. If I want a fly with a larger profile I'll switch to a standard steelhead Muddler. Joe Howells caddis stone and Mark Noble's After Dinner Mint are two other exceptional Muddler variations. As with wet flies pick one that you feel you can fish with confidence. All these patterns have caught thousands of steelhead from rivers around the world and are worthy of your confidence.
Muddler variations certainly aren't the only surface flies that catch fish. One of most interesting patterns I have used before is Bill Bakke's dragon fly. It has accounted for some very vicious strikes on the Umpqua and works great in any kind of water. It swings with a kinda side to side wobble. Bombers are exceptional choices natural with a white wing and tail and black with a white wing and tail are my two favorites. A common mistake I see with bombers is that the body's are improperly clipped. They should be clipped tight to the hook and streamlined in shape. Large bulky ones absorb water and hit the water so hard that they sink immediately and are very hard to keep on the surface. For best results trim them till they are small in diameter and tightly spun. You should also use the stiffest calf tail you can find. It's often best to tie the wing short and tie it in from the tip of the hair to gain the maximum amount of stiffness. Greased liners are exceptional surface patterns also and quite easy to tie. The nice thing about them as well as Muddlers is that they work great even if they are dragged under during the swing. I prefer a black body with moose hair for the wing and tail. Wulff patterns have also worked for many people in the past but I have never raised a fish on one. This is most likely do the fact that I fish them so rarely.
The presentation of a surface pattern varies little from that of a wet fly fished on the swing. Simply cast down and across and when it comes under tension the design of the fly will push it to the surface. You must remember to keep the rod tip high so you can drop it when the fish raises. Keeping the fly on the surface at the beginning of the swing before the fly comes under tension is always a problem. Dressing the fly with fly floatant can be a great help. Another good strategy is to make your casts with a greater angle downstream. This will bring the fly under tension faster without mending. To the contrary, on flat slow pieces of water it is common to have to lead the fly across to speed it up.
A few words about knots, any standards fishing knot that you'd use for a wet fly will work fine on a surface pattern. Adding a half hitch or two behind the head of a Muddler or the wing of a Bomber will ensure that it rides high all day long. When adding a half hitch hold the fly facing upstream and put the hitch on so that the leader comes off the fly towards you.
I hope this encourages some of you in your steelheading adventures to try some surface patterns. They do work and at times can be effective. Even when they aren't they are always fun and fishing them can really educate you on how current and drag effects a fly. I am sure there is a lot I missed but I hope this will point some in the right direction..