Blader-A
A very aggressive, hard-to-predict opponent, Blader-A will wait until the right moment to hit you with everything he's got.
A good strategy would be to keep your distance, dodge his attacks when possible, and then unload your strongest attack as soon as you can. If you're hit by Blader-A, don't despair; summon your bit-beast into the arena while you regroup.
Blader-B
A speed-demon if there ever was one! Watch out for Blader-B's lightning-fast attacks, stay well away from him whenever possible, and make sure to lead your target when attacking to avoid missing him.
Luckily for you, keeping your distance from this speedy adversary can sometimes have an unexpected effect; he'll be so preoccupied that he'll zoom himself right out of the arena!
Blader-C
As erratic and unpredictable as Blader-A, yet much stronger in defense. Blader-C can seem an insurmountable challenge, but don't give up just yet; mount a decisive, unrelenting attack, and you'll soon discover that his control over his blade is weak, giving you the advantage.
Waiting until Blader-C is near the edge is the best possible time to attack, as his lack of control will likely cause him to overbalance over the edge, and cost him the game.
Other Characters
For other enemy characters, a good strategy is to fight them once, take note of their weakness, choose the best blade to defeat them with, and try again.
For example, the "Kai" character is very attack-oriented; by choosing a defensive-based blade to fight him with, you can counter his attack and force him from the ring relatively easy.