Hi,
I primarily fish them in moving water and typically in a down and across manner. I’ll cast upstream a ways, then drift them down and past me, letting line out to extend the drift. I try to keep the line just about tight to the fly, but not quite, and look for subtle changes during the drift. Once the fly is in swing mode, hits will be easily felt and often jolt me from a contemplative moment.
Generally, I fish a team of 3 wet flies, so often I will have 3 spiders. Other times I might have a palmered fly on top (say, an Invicta or Soldier Palmer), a winged wet in the middle (Peter Ross, Royal Coachman, Greewell’s Glory, etc), and a spider on point. Generally, I’ll fish the runs and the riffles and work down towards a pool, fish through the pool, and out the other side. Often one picks up fish before getting to the pool, or just as you’re fly exits the pool and into the next glide. Occasionally the fish will rise up from the bottom of the pool to take the fly near the surface though. Most times, if the run is long and straight, I’ll just let out line and fish long, then slowly retrieve the line back by knitting it into my hand. Lots of hits using wet flies occur during this phase. If the stretch of water is a fairly short section, then casting upstream and keeping the fly line off the water (only the leader and the team of flies in the stream) can be productive. As the flies drift past, turn to keep facing the flies until they drift past you, as if tying to keep the line straight between the reel and the fly; this aids in keeping the dead drift with “just about there” line tension. If you are keeping the line off the water, don’t point the rod skyward, rather it should “point” the same way you would normally point it, just hold it higher up, with your rod hand up around your ears.
Most of my spiders have been tied on wet fly hooks, which are heavier than dry fly hooks. Because these patterns tend to have such a slim profile they will sink during the drift without the need to add lead or a bead. Casting upstream also helps to get them to sink to the desired level (whatever that happens to be on the day). Of course, on really fast water they don’t have much time to get down that far, but I generally am looking for “quickish” but not really fast, sections. Also, I tend to fish water that is about knee to mid-thigh deep, so even a fly on the surface is close enough to the fish that they may go for it.
I’ve started tying some spiders on lighter, dry fly hooks. Tied this way, on slower water with a nice smooth surface, you can gently drop them onto the surface where they immitate something stuck in the surface film (a dead and beat up adult, or a still born, etc). Used in faster water, these will simply not sink as much allowing you to fish near the surface over the entire drift, which can be useful if the fish are feeding on or at the surface. The heavier ones may sink below the feeding fish.
If you tie some on dry fly hooks, I would fish them just in the surface film letting the wind blow them around. Some heavier wire hooks could be left to sink slowly, then slow retrieve to make them swim to the surface to emerge.