The Granovetters have a relatively easy book out called A SWITCH IN TIME in which a suit in dummy is deemed to be the OBVIOUS SHIFT according to 11 very obvious rules. Therefore, at trick 1 you discourage a continuation if you can stand the OBVIOUS SHIFT (OS), or you encourage if you can't stand the OS, or you play an unusually high card if you want the UN-OBVIOUS SHIFT (usually dummies best suit). There is only one case when you give suit preference at trick 1 and that is when trumps are led. This defensive system is used by many experts and is also used by the expert panel of solvers in the BRIDGE WORLD magazine. Playing in a regional tournament the bidding went 1c p 1s p // 3s p p p. Partner led the heart king promising the ace (we play rusinow) and dummy hit with  s AQxx h xx d Kx c KQJT9. I held s Kxx h JTxxx d xxx c Ax. I signalled for the UN-OBVIOUS SHIFT with the heart jack and partner shifted to the club which I won and exited a club. When declarer took losing spade hook, I got partner in with the heart and got my club ruff. We were the only pair to get a plus on that hand in the whole field.