I'd say one of the first things (if not the first) I look for in a submission; I'll read the first paragraph and see if it's engaging me voice-wise, and know I want to read more. Here's a throwback, and another, to a few posts I wrote all about it!
Tip: you can use the "search" feature of this blog to view more, if you're ever looking for something specific!
Unsolicited Twitter pitches.
Certainly, if I'm participating in a Twitter pitch event, it's a-ok to pitch there. Outside of that special event space, however, no way. It's pushy and smells of spam (yes, I mean junk mail, but you should also picture a stanky wave of SPAM wafting up to me from Twitter from each unsolicited Twitter pitch, because that is exactly the face I make when I see one).
Twitter is a powerful networking tool, and should absolutely be used to your marketing advantage - but in the right way. Don't ever be a spam-bot. I have submission guidelines for a reason.