Don't forget the power points
Only when a nation builds factories, places flags, and in the end plays "taxation", can it advance with its power points. It may not be possible to avoid conflicts with other nations, but nations who set up troops and wage war all the time, will not be successful in collecting many power points.
Be careful when concentrating on one nation
It may be tempting to grant bonds exclusively to the nation in which the player has control, in order to stabilize the government and to enable the nation to build factories and pay interest.
But this may be a dangerous strategy, if no other investors invest there, and no one else is interested in seeing the nation flourish. The nation will be attacked sooner than expected.
Take care of your money
Of course it is important to develop the nation in which the player has control. But nonetheless one should not forget the role of being an investor desperately in need of money in order to win the game. Entering the Investor space on the rondel may slow down the nation, but it usually is the most efficient way to get money.
Use the Swiss Bank
The Swiss Bank is very useful to get hold of many smaller bonds with higher interest rates. And if the preconditions are fulfilled, it is mostly a good thing to force a nation to stop on Investor and pay out interest.
The end of the game may come surprisingly fast
Nations who are well developed, owning many factories and tax regions, can progress on the scoring track very quickly. A nation needs only 4 factories and 7 tax regions to gather 10 power points. Therefore it can easily happen that a nation that is behind, suddenly rushes ahead and ends the game by reaching 25 points.
How many turns does a game of "Imperial" usually take
A typical game of "Imperial" takes about 120 individual turns, i.e. 20 turns per nation. The game usually ends after the winning nation has entered Taxation four times. However, this does not necessarily mean that the player controlling that nation wins the game.