Dru,
You can book a Beat by phoning the Hotel and speaking to Nicky or Nathan. The Beat you fish is yours for the day but can be shared by a Salmon fisherman (I think though in practice I have never experienced this). Each Beat apart from 1,2,3 and 12 has an opposite bank so 4 and 5 are opposite,6 and 7,8 and 9 (Sir Archies private beat) and 10 and 11. So if you book say 10 there may be another Trout angler on the opposite bank. Main Trout fishing activity is April and May with less for the rest of the season. Chances are if you go in the week you will have several Beats to choose from.
You cannot wander onto another Beat during the day and you can wade(Chest waders best as Don can be deep and powerful).
A 6 and 7 weight rod is adequate but a touch on the heavy side. If you get into river fishing more a 9' rod to take a 4 or 5 weight will be more enjoyable and still have enough stick if you hook into a large fish.
What patterns.........it's like anywhere on a river,fish what is hatching or falling into the river. Scan teh surface film if the fish are rising but you cannot discern what they are taking. Carry Black Gnats,Beetles,various Olive patterns in size 14 (Olive Uprights)16(BWO) and Spinners in the same sizes. Also Klinkhamers with a fluro yellow wing for very late evening fishing. If it's you bag a selection of Czech nymphs when things are quiet and some spiders should do the trick.
I am not on the water much at this time of the year but I know Ben Dixon (and others) are so they should be able to advise you as to what is hatching,
Good Luck,
Richard