As for correct density of fly lines, again time of year will decide this but a floating line, a sink tip or intermediate, and a fast sinking line (2/3" per sec) will cover most eventualities. Care should be taken to balance your fly rod with the appropriate weight of fly line to maximise your water coverage.
This really is one for the individual beats to advise on. Bring a selection of flies, small ones for smaller rivers, warmer temperatures and lower water conditions, larger ones & heavier tube flies for the opposite conditions.
A fully automatic lifejacket is a necessity when either fishing from a boat or wading in a river. Many beats now provide lifejackets and you will be strongly recommended to use them.
Some form of eye protection is also recommended, whether in the shape of polarised sunglasses or clear safety glasses to protect your eyes whilst fly fishing.
A strong, sturdy wading stick is also an essential item on an angler's 'must have' list. Make sure the end is weighted and has a rubber stopper to minimise noise and vibration as you wade down through a pool.
For a general guide to safety click here