The first week in June is rather early for the salmon but you might find sea trout at
Steinish, just outside Stornoway. Permits from Underground or Sportsworld, Francis St., I think.
If it's brownies you're after then tell us whereabouts you're staying and how far you want to drive/walk. There are hundreds of lochs available. If you're in town, pick up a copy of Norman Macleod's 'Trout Lochs of Lewis' from Sportsworld, it's a little dated now but is still the best fishing guidebook available for the island. Neither the grid references nor the fly choices have changed much over the years.
The usual thing here is to fish three flies with a bushy bob to make a fuss on the surface but, of course, nymphs and buzzers work well too. I've never had success with English reservoir lures like the Cat's Whisker, Zonker, Montana Nymph, etc., but have caught a few fish on mini-lures when experimenting.
Dry flies come into their own on an evening rise, but a lone dry like a Daddy can work any time - great for teaching kids as the savage surface takes can be heart-stopping.
If you get a bright blue-sky day try a blue fly with a bit of silver (the Teal, Blue and Silver is great -especially if there's a chance sea trout are about). On darker days I tend to fish a darker fly on the tail with a bit of an attractor on the middle dropper.
Sizes; 10 to 14, depending on the wind and wave.
Recommended Flies:
Wets: Ombudsman, Claret & Golden Olive Bumble, Black/Blue Zulu, Dabblers, Grouse/Mallard and Claret, T.B.S., mini-muddlers, Peter Ross, Black Pennell, Bibio, Butchers.
Dries: Daddy-Long-Legs, Grey Wulff, Parachute Adams, CdC emergers, wee black things.
Hope that's some help.