One of the primary complaints I hear is the inability to attack a suit due to being short suited. Although this can slow or hinder plans, problems like this should be anticipated and dealt with. It's highly unlikely that mastery in all four suits will be achieved, so plans should be flexible enough to work with the draw rather than fight it. I'll list three methods for dealing with a suit while having few cards in it.
Wait and See - Attack other suits and wait for a better draw.
Prussia may use the suit you are worried about on another player.
Austria can best employ this strategy, as the pressure is not on an early attack.
Slow, other more aggressive players may beat you to the objectives.
Very bad strategy for Russia, rarely can it afford to wait for better cards.
The draw may never turn your way.
This is the first strategy most players employ when confronted with this problem. With proper application it can help in the short term (1-2 turns), but as a long term strategy it could mean waiting until it is too late.
Exploit Borders - Sit/attack on the suit borders, or position so that you can counterattack across a border of the suit you wish to attack. This leverages two or three suits against one.
Very effective against an aggressive and unwary opponent.
Can rapidly collapse the defense of a suit in a single turn.
Often the threat of this is enough to allow aggressive maneuver even when unable to challenge in a suit.
Very effective for Russia which needs to push as fast as it can.
Will require the emptying of one or both of your suits, which could result in disaster later.
Higher risk than waiting for cards, the opponent could have both suits covered.
Requires a mistake by the opponent.
Against an unwary opponent this will almost always work. Skilled opponents will be very aware of what suits they are using against which players and will not let their suit be depleted this way. Against these skilled players this is more of a maneuvering tactic than a way to take a suit.
The Hammer - Stack generals to get an overwhelming local superiority in armies and attack in the suit you wish to threaten. Retreat at low losses (-1, -2 or -3 if necessary) as soon as possible and repeat the next turn after replacing losses with cards from other suits.
Over time will break down the defense of any suit.
Very effective if holding a lot of low number cards and/or reserve cards.
Be careful that the possible retreats will not allow the attacking generals to be surrounded.
Opponent can force you to use more cards than you want to by playing to 0.
Can take time if the card disparity is very large.
Requires some cards in the suit and at least one reserve card, or else the attack is probably too dangerous.
If it's obvious that the player won't be baited into #2, and #1 will take too long this is best resorted to quickly and decisively. Two or three turns of this at a 10+ army advantage is usually enough to change a suit disadvantage into an advantage.
I'll add another con to the Wait and see approach. When executed poorly, you are transmitting your weakness to your opponent.
Pull off a bluff that your weakest suit is your strongest, and suddenly your hand looks great!