Well, as obvious as it is, please head over to the official website of the game and read their beginner's guide.
You can find it here -->
http://global.netmarble.com/minifighter/Guides/ViewAllList.aspThere's alot of information there, so I'd highly recommend reading it while waiting for the game to finish downloading.
Apart from that, I've got a few tips off the top of my head with regards to the pvp aspect of the game:
1) MOVE. If you're standing still, you're usually in a bad position unless you've got insane reflexes. Not moving = free for crossups, fireballs, combos, etc etc etc
2) BLOCK. This is probably the most important aspect of the game. If you don't block you're a sitting duck for just bout everything the opponent throws at you.
3) Learn your character's combos. Go to the arcade and test out which skills combo best with which so you don't mess up a juggle opportunity.
4) Get used to the pace of the game. For newcomers to fighting games, the pace of this game can be quite unsettling initially, at least for pvp. Generally speaking, if you're finding it hard to keep up with your opponent, you're on your way to losing.
That's just about all the information I have right now. Feel free to contribute to the thread too!
If anyone's up for games lemme know. either pm me here or find me in game!