I am going to be hitting up an instance with my guild so Tricks of the Trade is going to get some testing (and may be a life saver given I'm a few levels above the tank) so a macro is going to be required. Most people have recommended setting the tank as the focus target and then having a macro like this:
#showtooltip Tricks of the Trade
/cast [target=focus] Tricks of the Trade
However if I'm going to be sapping things, I tend to set the Sap target as the focus target so that Class Timers can show me how long is remaining on the crowd control. In this situation the following macro may be more useful:
#showtooltip Tricks of the Trade
/target "Tank"
/cast Tricks of the Trade
/targetlasttarget
The only disadvantage here is that there will be some loss of white damage whilst I'm not targetting the mob, and will need to be careful about how combo points are preserved when switching targets.
Finally I'm planning to switch back to mutilate, a blacksmith in guild has agreed to make me two Saronite Shivs which appear to be awesome for PvE so it'll be fun to go back and see how the changes in the Assassination tree pan out.
(Thanks to One Rogue's Journey for the details on the macros)