For the most part of May the banks are still the place to be. As a rule the fish are high in the water feeding near to, if not actually from, the surface. Of course all rules are broken at some point and I can think of several seasons where the Booby was the only successful way to go. But assuming we are given a pleasant month, the sort which textbooks write about, we can be fairly certain that we will be using the floater and will only have to resort to the intermediate during really bright days, when the fish are down a little ways. Not only that but we will probably be able to dispense with the leaded flies and fish with light-weight patterns or gold heads at the most.The first and, perhaps, most successful method, is to fish a team of buzzers dead drift in the current, covering fish as and when they appear. Simple seal fur jobs on the droppers with, perhaps, a feather type on the point, which should sink a little quicker and help with our casting.
Perhaps less successful, but in my opinion certainly more enjoyable, is emerger fishing. If trout are rising then they may be induced to take a dry.
The cream of the fly fishing in May is, without doubt, the Hawthorn fly. Hawthorns indulge in a great sexual orgy all about the bank-side and often end up in the water. Not being aquatic they often get stuck there and trout love them. Fish these big dries damp, that is to say stuck in the surface, cast to rising fish and expect fantastic results. When the Hawthorn are about and the trout are gorging themselves the fishing is really hot. If you don't have hawthorn patterns in the appropriate size you will not catch fish. Full stop. Carry them.
Towards the end of the month fish will begin to rise well to sedge flies. Early on in the season it usually pays to fish pupa imitations as opposed to the dry sedge. Dry sedges are not normally taken well during the month of May. Perhaps it takes a while for the fish to become accustomed to them. I dunno.
Sedge pupa move quite quickly through the water, so that is what you should be doing with your flies.
Autopsies of trout also feature caenis. Now here is a conundrum for you. The standard approach to a caenis rise is a black lure fished high in the water. This is always the first line of attack. Occasionally it is essential to fish with caenis duns and spinners. It doesn't happen very often, not on stillwaters. When it does the trout are often within inches of the bank.
Back in the days before I knew of the success of the black lure, my approach was small hot orange thoraxed pheasant tail nymphs, with a wet white-winged Wickham's on the top dropper. The method relied on accurate casting and not giving the fish much time to think. I figured that the Wickham's was taken for a super sized caenis. Sort of a mother of all caenis'. I guess it's somewhat like absent-mindedly snacking on a packet of crisps, only to find a potato halfway through the pack.
If you are fortunate enough to fish a water with a population of Upwings you will come across a hatch of lake olives or possible Mayflies. The lake olive nymphs feeders are dealt with using pheasant tail nymphs. Small darting movements. For dries I use wingless Greenwells, in parachute and standard hackling, and hares ears for the Emergers. I have failed to fish a good hatch of lake olives for some ten years.
For mayfly feeders, and I have never come across a good hatch of mayfly on the lakes I fish, only rivers, and never as good as the stories of those exclusive waters I have read so much about, try using a grey Wulff for the dun and Walker's Mayfly Nymph.
Sometimes the fish will gorge themselves on daphnia. Daphnia are very small creatures which are all but impossible to imitate. The only recourse is to knock the trout out with a lure. Surface feeding trout are taken with hot orange lures stripped very fast. Deep feeders are taken from the boats.