Before the permanent late shift was introduced three years ago (which I volunteered for as soon as the form became available), I always tended to plan my vacation for early shift weeks. Since the majority of the people in most departments prefer to work early shift and thus tended to plan their vacation for late shift weeks, there were usually enough slots available for me to get my request fulfilled.
I was promoted last December, so this past year is my first with the company where I've been able to get whatever vacation I wanted. Instead of competing with 100 other people, there's now only 1 (out of 3 others who share my job) that's been in the building longer than me, and so has first dibs at weeks. It's pretty easy to work it out between ourselves before we give in our requests, though
So a few of the same rules, a few different ones. For regular employees, requests need to be in by January 15th. If they are, those are doled out based on seniority. You're only guaranteed 2 weeks in "prime time" (basically June, July, August). Anything submitted after January 15th is given out first come, first served based on availability
I knew a woman at Target who was forced to use up her vacation time before she could qualify for maternity leave. Then they denied the leave because she technically hadn't been at work for two weeks beforehand.
Also, if you become sick during your vacation and you turn in a doctor's sick note, it means that you don't lose your vacation days, because according to the law, vacation is intended for recreation, not for recovery from sickness or injury.
No, they prioritize vacation during school holidays for employees with school-age children. Also, only three of the six weeks during the summer holidays per employee so a larger number of employees can get their requests fulfilled.
In my nine years with Amazon, only one of my vacation requests (not counting requests for single days) has ever been denied (with an alternate option offered for a mere week later). It might have helped that I have always tended to plan my vacation against the grain.
We also have a legally guaranteed minimum of at least 24 vacation days per year, and the law mandates that the vacation should be granted in one stretch "unless urgent reasons on behalf of the company or the individual employee make it necessary to split up the vacation". The most common valid "urgent reason on behalf of the company" would be "multiple employees have requested their vacation days for the same period, so the employer has to organize everyone's vacation grants equally".