Mistake 2: Reaching out without understanding the industry niche
If you don't know what you're talking about, the blogger is going to notice. You don't need to know the innermost secrets of the industry that you are marketing, but you should at least understand:
For example, if you are responsible for the blogger outreach effort for a new bakery ("Bobby's on Main!"), you might approach a baking blog like JoyTheBaker.com. If you say something bone-headed like "I love the smell of muffins broiling in the stove," Joy is probably going to ignore your email. (Actually -- that one would probably be a keeper.) But shooting the moon is a tough sport to play in blogger outreach. So play it safe and only talk about what you know. If you're about to start a new full-time job, at least read the Wikipedia page about your industry before your first day. And do your best to stay current.
Extra embarrassing: Misunderstanding the point of the whole blog. Don't email a vegan blog with coupons for discount chicken.