Is there still time to get another vote in for the "just be yourself" ticket? Seriously, it sounds like your shy, and that is very cute to the right girls. My problem is that I worry about things way too much when I'm talking to a girl. Instead of considering myself talking to a cute girl, once I push myself into the situation, I seem to feel like I am being "confronted" by a cute girl, rather than flirting with them. haha. But, its okay, who cares? Its YOUR mind that you live in man, and that makes the world yours as well. You aint sharing my consciousness. You have your own consciousness. So, don't worry about anyone else's judgements of you, because they can't climb into your head and hurt you emotionally, unless you ALLOW them to. Feel me? It is YOU creating the worries, the anxiety..
When I see a cute girl, I smile at them, and I shoot my head down, and then, I FORCE myself to look back up, and, if they are walking and smiling back, then I PUSH myself to approach them, and by then, I'm not really thinking at all, you just have to say hello, say "hey" and.. they will say hello, and.. you'll say.. whatsup? and, they will laugh, because, your acting like you already know her, haha, and.. thats how you meet a cute girl. You don't have to compliment them if you can't due to your shyness, just, be yourself!
One thing that helps me personally, is to go into the conversation goofily. If you approach a cute girl and say "ello mate!" with a big smile, who knows, maybe they will laugh, put their guard down, bring themselves out of that auto-pilot mode and into giggly aw this guy seems cute mode. Once you introduce yourself as goofy and carefree, its easier to portray yourself as carefree.. You just don't want to go overboard, but, if your a normal person, its pretty hard to go overboard, haha. (and coincidentally, its basically what we all worry about, without knowing it, y'know?)
And if you REALLY want to get into those corny "secrets" that get passed down from brother to younger brother or older friend to friend, haha, the best "pick up line tip" is probably the most simple one. Use your surroundings. If you like her hair, walk up to her and say "Hey, I like your hair, its cute!" DON'T walk up to her and say "Hello! I like your hairstyle, its beautiful. Does it smell good!?" NO!! NO SMELL COMMENTS! This is something EVERY GUY MUST RESIST!! lol. Smile at her, WAVE at her, if she kinda laughs and waves back hesitantly, shes already down to fuck you down the road bro.

Like I said, use your surroundings. If shes got a bestbuy bag, just approach her and say "heyy I just came out of BestBuy, I was looking for a new set of earbuds. Do you know which sound the best?" Or if shes waiting at the bus stop, ask her if there is a bus running to [insert part of town here] Then, go from there.. The truth is, you want a conversation. You don't go strait to "I'm sorry, I would never usually do this but, your just, your really cute" No. That might work at a club, when your both buzzing and looking to cuddle with someone as it is.. But if you see a cute girl at the mall, you just use your surroundings.. Her shopping bags, what store is she walking out of, or walking toward, ask her if she knows where payless shoe store is.. You want normal conversation. Its the icebreaker you need.

If you yourself are a bit hefty, and you like the hefty girls, you will basically have to fight them off after you've approached them, so, maybe you can start there?
Finally, the signs of "rejection." Yeah, you kind-of need to know them.. I guess. 8) lol. If you ask her a simple surroundings question, and she keeps walking forward, without really looking toward you, then she's already looked you over and she doesn't like what shes seen already bro. If you have experience, you can try again without getting into too much trouble, but for someone new to flirting thats probably not the best idea. Just turn around and walk. Don't stop in your tracks. You'll feel rejected and she'll be laughing at you while you stand in one spot gathering your thoughts.. Are you a sadist? If you get turned on by humiliation then your good to go man. Just don't use it as a pickup line. You can't start the conversation with "hello, i noticed you looked like a bitch, can I kiss your feet?" YOUR DOING IT WRONG. lol. And if your the dominant type, you can't approach and ask if she'd like you to tie her up. She'll just run away screaming. :/ See, everything has its own order man. The kink needs to be introduced slowly, like the gas in a kitty euthanasia chamber.. No worries, you'll be blowing coke from her asscrack in a month or two if everything goes right.
Hope this helps you.