by Jota on Wed Jun 21, 2006 5:53 pm
I think one popular rule of thumb is that it's good to weaken the strongest player and to strengthen the weakest player (unless you are the strongest player, of course!).
Note that this doesn't necessarily mean that you should be attacking the big guy: if you can arrange it so that someone else has to expend their armies doing it (drawing attention to themselves and incurring the leader's wrath in the process), all the better.
Also, this rule might not apply in cases where you have the chance to wipe someone out completely: sometimes a nice influx of cards is more powerful than any other strategy.