And yes, your order of merit (class standing) plays a role for both service selection and selection of ship or pipeline school date start. For example, someone near the bottom of the class may still get their #1 choice, Surface Warfare, but not get their dream ship and location, getting an amphib in Norfolk instead of a Burke destroyer in Pearl Harbor.
Fall of 1/c year is generally service selection time, and after winter holiday, ship/school date selection. Some mids hear earlier what their service selection is, such as early select submarines.
Finally, YouTube is also your friend. Here is a sample searching on "USNA Class of 2016 service selection":