Fishing breaks are your best bet, Simon can advise on which beats will suit you best, and make sure he knows you're a newcomer to the Test so you don't end up with a difficult beat.
Advice wise, you'll be able to see the fish so should be able to work out what they're feeding on, be careful you're not seen, and present the fly carefully. Any clumsyness in approach or presentation will be punished, so take your time, make sure everythings sorted and you know what you want to achieve before you cast, and enjoy it. And don't spend ages casting to one fish, if nothings happened after 2/3 flies move on to another one, and don't spend an hour casting to a carp/pike like some clients I've known!
Flies wise, PTN, Gold head PTN, Small/Large klinkhammers, and BWO patterns will see you right for 99% of fish. Alas, I hate to say it, but include Daddy long legs as well as it probably catches as many fish on most beats as anything else!