"I mean, when you ask "What do I need to include in a press kit", you're treating it like a homework assignment. The question is, what's your goal with a presskit? You want to get signed? Alright, you need to ask yourself: if I was a record company, looking to make some money by selling some great music, what would I want to know about a band who wanted me to spend my money on them? What kind of things would convince you that band x is a worthier investment than band y? "
Well I'm being picky I guess but it's not about 'great music', it's about selling units. If you can convince a record label that they will be able to shift tens of thousands of units by signing your band thern you'll get signed. Convinincing them to sign you is about showing your band can sell plastic units, not that you make great music, that's almost irrelevant whether you like it or not.
So, if you can demonstrate that you sell records already, or you get lots of publicity and are always in the news, or you sell out shows all over the place, or preferably all those things, then they'll queue up to sign you.