I messaged about 13 people last night and got 4-5 replies today. I don't think about opening lines, I just look at something in their profile I want to talk about. One girl saw Stardust so I said to her "I thought I was the only one who saw Stardust! I tell my friends about it and they look at me like I'm crazy." This led to a conversation about Robert DeNiro, Firefly, Doctor Who and Torchwood, D&D, Magic the Gathering, and nerdcore hip hop. She's actually listening to my stuff on SoundCloud as we speak.
With another girl, I talked about tattoos. She's not as responsive as the girl above, but it's still a decent conversation.
Another girl I identified the camera she was using in one of her pictures, noticed she is going to school for photo journalism, and interned at a music magazine. My opening was something along the lines of "I love the 5D love in your photo! What lenses do you regularly use?" yadda yadda. Her reply back was a comment about how I picked up on the camera by its body and we messaged back and forth about music, magazines, and filmmaking.
You have to remember that women are human and share the exact same interests as you. Also remember that people like to talk about themselves. Just talk to them like normal. You don't have to craft some weird, epic paragraph to hook anyone.
Oh, to help with replies, sort your matches by their match percentage and friend level then just cruise and figure out who you want to talk to. That really helps.