Dirty underhand tactics
Depending on how you like to play, you might like some of these...
The Sticky Bat Probe - the original underhand tactic. You need a sticky bat (obviously) and a ball, and you must be moving towards the opponent you wish to probe. Simply move so that the ball is behind their bat (preferably over their floater balloon) and release. Catch the ball and repeat until the opponent is going down.
Wrap - it seems to me that the computer isn't so cautious about wrap as experienced humans are. So if you're playing against computers or newbies, try activating Wrap and hitting the ball so it wraps around and towards another player. They won't see it coming but may still be able to block it if their reflexes are good.
Football - Charge! This is the best piece of advice I can give you. You start off with a bit of Power anyway, and in subsequent matches you will have carried over power. So simply charge straight at the enemy goalie and probe him. If you get the ball first it's easier, if he gets it he will likely shoot at (read: to) you.
Dogs Extreme - Use Inku. If you want to be risky, you can try using Moon or Pook too, but they are vulnerable to mines and Laser Extreme, so be careful. Alternatively, try using BCM if you think you have the reflexes to hit the balls at least once each.
Any situation where you're moving VERY fast - use Jera. Laser Extreme plus some pace generally equalls a lot of players with no bubbles.
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