Programming 3, a push in the right direction needed

[Avery17]

I could use some help. I have read through all of the programming 3 mission threads and don't understand how I should go about brute-forcing this one. Should I try a dictionary attack? Random string attacks or what? Should I try bruting the individual characters themselves?

Please, any help would be much appreciated. I spent most of my morning writing up the decryption script in PHP, it works perfectly. I just need some help working out a smart brute forcing method.

Edit:
I think I just got some ideas, anything would be nice though. Thanks.