OK mate,
If you're not used to starting conversations with strangers, the more you go out and practice, the better you will get. For example, i just start talking to people, i'm used to it, I don't need openers.

You first need to realise it doesn't matter what you first say, as long as you keep the interaction going as you like, its all good.

However, during the night, you will be going in your head thinking "what do i say?". So, its ok at your level to use openers. You can use anying, for example "hey, you seem quite cool, i had to speak to you, having a good night?"...just have something like that which rolls of the tongue and let the chips fall as they may....then keep the convo going. It takes practice....

One more thing, lower your standards on what you think is cool to say. Have you got mates? Talk to strangers like you would talk to them, well that's the aim anyway. I know it's tough at first, but plow through. Good luck!!!