Spot the Signs. Do you have a good relationship with your manager? Is he or she relatively reasonable? Do you have regular one_on_ones where you talk about your career goals and growth? If so, it's likely that your boss will accept your resignation with grace, help develop a plan of action for your last two weeks, and maybe even attend your farewell happy hour.
On the flip side, if you loved your job, your coworkers, your boss, the cappuccino machine, everything about the place, don't write page upon page waxing rhapsodic about all that you're giving up by leaving. A brief, heartfelt compliment to the company, or a thank you, is fine.