Wilbert is on the right track.
I could write a book on how to fish the midge pupa.
In still waters the chironomid is probably the most important part of a trout's diet. They eat them in vast quantities from the bloodworm on the bottom to the pupa which swims in fits and starts to the surface where it eclodes. It is during the surface migrations that trout take them in such vast quatities.
And I catch more trout on buzzer imitations than any other pattern.
Here's how I fish buzzers.
In largish reservoirs I use a 7 weight forward taper floating line. At the end of the line goes a 12 to 20 foot leader made from 6lbs fluorocarbon. On the leader there is a point fly and two droppers. The overall length of the leader is dependant on the depth of the water I am fishing.
Generally speaking the droppers are positioned on thirds of the length of the leader. The point fly is often a heavy bloodworm imitator. The weight helps the long leader to turn over.
For buzzer fishing I like the wind to be coming over my left shoulder being right handed.
If there is no sign of fish near the surface, I cast out and let the leader sink right down. Often I will leave the line alone for at least 5 minutes. Trout will often take a static buzzer pattern
Then I will start a very slow retrieve using the figure-of-eight and drop style. The line is run over the second finger of my right hand. During the retrieve, I also allow a loop to develop below the rod tip. Detecting takes is a combination of feel and sight. You either feel the line do something different with the second finger or you see the loop of line perform differently to what the retrieve is doing to it. Slack liners are common.
Often of course, you get a good solid take and equally often you don't. Watch that loop of line like a hawk.
In mid retrieve, I often stop retrieving and allow the flies to sink. Then start the retrieving all over again. A trout often takes your buzzer as it rises to the surface.
When fish are actively taking buzzers just under the surface you will spot two types of rise forms. What you will see is either the "Shatter" rise which appears as a minor detonation under the surface or the flattening of a wind caused ripple; or the classic "head-and-tail" rise where the dorsal fin and top lobe of the tail fin break surface, similarly to what a dolphin does when it swims.
This is the time for a shorter leader and faster retrieve. It is also the time for very accurate casting, judging where the trout might be after the rise and also estimating how deep it might be. The correct combination of these three functions will catch you lots of fish, but it does take great skill. The more you do it the better you become.
As regards patterns, I tend to use those which are tied with soft materials as I believe the trout hang onto them a little bit longer.
Hope this helps.