A: It starts with a good foundation: a solid subject line, a tantalizing subject line, a subject line that promises a thousand times more than it delivers. Then, and only then, can the art of spamming begin.
A: DO: Include a picture of a kitten. DO: Use a font that's bigger than the body text. DON'T: Use Comic Sans. DON'T: Link to a PDF that's just a picture of a cat.
A: Only if it's a product that's 100% not what I claim it is, and only if I've been paid to say that it's not what it is, and only if I've been paid in advance for that specific lie.