I heard someone mention a VERY sneaky move...If player A has a large force guarding one of their continents, you can attack it for a while to weaken it, but not take it. Then perhaps player B will notice that the continent is weakly guarded and capture the country to prevent A from getting the bonus. When A looks at the log, he/she will only notice that B captured the country, so unless A was watching your turn he/she will have no idea you were involved. This allows you to break up the continent and pit two players against one another while looking completely innocent! Note: I did not come up with this devious plan, but I like it for its simplicity and its double benefit.

A more common strategy was implemented against me by one of the top ranking members of CC. It was a freestyle game with no double turns allowed. We were the only two left in the game and he used all of his forces attacking as many countries as he could (and spreading himself very thin). I had just finished my turn, so I was watching while he played, and then began my turn right when he finished. The second I began to play he started his next turn as well, which allowed him to reap the huge bonus for all the continents and countries he had taken on the previous turn. Not only that, but he waited for me to place my men before he made his next move, so he knew where to best place his own men. I'm sure many have seen or heard of this (especially since it was recently mentioned in a thread) but for beginning players its something useful to keep in mind.
I have a few more good strategies I'm willing to share, but first I would like to open this up to all the other tacticians who frequent this forum...