The proper use of the "&&" is in continuation of a previous statement. The trendy kids tend to misuse this punctuation by throwing it in everywhere. It should not be used every time one uses an ampersand. It's really something which can be used more to reply to something someone else said.
"last night we saw a movie
&& picnic-k-ed in the park."
alice: "& tonight everyone knew
something was off --
tall kid giggled about getting drunk..."
nikki: "everything is always off.
& everyone knows it.
&& getting drunk isn't funny.
(okay, well, sometimes...)"