well, depends on if i'm feeling ghetto or not.
if i am, i will just wait for a hot girl to walk by and grab her by the arm. i'll just say she's hot and start talking to her.
if not, i'll start a convo by saying, "wanna hear the worst pick up line ever?" they usually say sure. then i reply with...
"ever fuck an ugly guy with a big dick?" (no) "do you want to?"
but it kinda backfires because i'm not really ugly. so they just chuckle. plus it makes you sound humble by calling yourself ugly. you can use it to fish for compliments.