We're not staff and we have never been nominated for anything before.
What others have said is typically staff will contact you via internal PM saying that they want to feature you and they need you to make up some art first. This is usually for the Spotlight. We've also heard that staff will write and ask for a creator to compress several pages into a single larger episode prior to being made a Staff Pick.
Daily Snack just happens w/out warning. Other artists have told us that their notifications start going bonkers and they wonder why suddenly they are having 1000s of views and 100s of subs and comments and then they realize they received a daily snack.