Manage your stock of cubes wisely
Cubes that are left unused by the end of a season can be used in the next season.
Thus, a player who saves up more cubes than their opponents will have more at their disposal for the next season, which will especially be useful for the fourth season, when the game region is larger.
Do not fight uselessly
Remember the first two players of each area are sure to earn something (either a parcel of a place in the Museum). Its is therefore useless to accumulate cubes in an area where you are only threatened by one opponent, or to try and beat an opponent at all cost when both parcels are interesting.
Keep the Museum in mind
If you place no cube in the Museum, your cards will only yield one point, which is not sufficient to win the game.
Try and secure an access to the Museum with a 'Sir Brown' card, or "sacrifice" a few parcels (even strong ones) at the right time (for instance, when there are only two players in the area, and the card you are sacrificing will not be of benefit to anyone).
If you stop placing cubes too early, you run the risk of seeing other players take your majorities. Conversely, it is useless to waste cubes if you think the situation is safe enough, all the more so since being the first to pass will make you win every draw.