Note, this was the first battle that I actually had a bit of trouble with, as it's the first tough battle, and, on my first time through the game I wasn't collecting many DPs so my magic was weak. Per usual, I suggest going heavy on the "Protego", to protect yourself from the thugs. Also, I believe "Stupefy" is a great spell to cast. Even if it doesn't do much damage, it does stun the enemy, allowing you or an ally to hit him. I'm also a fan of "Expelliarmus".
While fighting, keep in mind that your friends are there to help you. If you feel overwhelmed, step away from the battle, perhaps behind an obstacle of sorts, and take a breather. Also, be sure to move around to avoid the casts of others.
If you fall from battle (and don't get back up), you'll be sent to the Hospital Wing. Return to the Courtyard and move the package to try again.