Community Nightfall strategy

General

Because of the unique anti-stalemate function in Nightfall, if your team's cart is ahead of the opposing team's cart near the end of the round, it may pay off to pull back and simply defend your cart. In doing so, both carts will continue to roll forward on their own. This strategy doesn't work on Stage 3, as there is no time limit.
Stages 1 and 2 feature buildings separating each team's spawn from the central area, rendering sticky jumps and rocket jumps rather ineffective. However, Soldiers and Demomen can jump directly to the cart on Stage 3 with a well-timed blast.
On Stage 2, team members should initially focus on pushing the cart up the incline. The cart will roll back if it does not reach the top, and this part of the map can become a choke point if the opposing team sets up a successful defense.

On Stage 3, Pyros should make use of their compression blast to push opposing team members off their cart. Even if they don't get pushed into the pit, forcing them to climb back up to the cart costs them valuable time while your team pushes.

Due to the tight corridors, Engineers equipped with the Gunslinger can deploy Mini-Sentry Guns to great effect on certain parts of the map, namely around corners. They can also provide distraction while teammates flank the opposing team.

Stage 3's open nature is very friendly for Snipers, with long sightlines. On Stage 1 and especially on Stage 2, Snipers may be better off equipping the Huntsman, along with Jarate, to do more close-range damage.

Spies can make effective use of the tight corridors of Stages 1 and 2 to pick off enemies not on the cart.