Well, using a mix for Star Fleet Battles and TV and movies, I think that Klingon vessels would make slashing attacks in formation if possible. Forming ships in 3-ship squadrons and coordinating fire to take on larger opponents. They have weaker rear shields and most of their firepower is forward facing, so their fighting style is very aggressive, while not being above using cunning to win a battle. They would also try to board an enemy vessel as soon as possible and take it in hand-to-hand combat (more honorable and glorious).
Romulans would use more stealth and guile. Sneak in under cloak, then hit with plasma torpedoes, then finish the target off with disruptors and photorps. Probably go for the decisive battle strategy (think Japanese Imperial Navy in WWII).
The Federation is more reserved, they will not fire first (unless it's wartime) and try to disable instead of destroy the target. They will not start a fight but will finish it. Federation ships will sacrifice themselves if it will save lives.
"Retreat?! Hell, we just got here!", annonymous American Marine, WWI
"Gravity is a harsh mistress....", The Tick