A fall display isn't the destination. The door is. Everything on the porch exists to send someone's eye toward the entrance and make the house look like a place worth walking up to.
That sounds obvious, and it gets ignored constantly — usually by displays that are impressive on their own and leave the door out of the picture entirely.
The test
Stand at the sidewalk. Where does your eye land first, and where does it end up?
A working display takes the eye in at ground level, moves it up through the arrangement, and delivers it to the door. A display that isn't working holds the eye in the pumpkins and never gets there, or it lands on the door immediately and then wanders off to the sides.
If you can't find the door in the first two seconds, the arrangement is competing with the thing it was supposed to introduce.
Taper toward the edges
The simplest way to build in direction is to make pieces larger and denser near the entrance and smaller and sparser as you move away from it.
That's the opposite of what most people do instinctively, which is to put the biggest pieces at the outer corners where there's the most room.
Big at the middle, small at the edges. The taper itself points inward, and the eye follows it without being told.
Frame, don't crowd
Corn stalk bundles standing at the outer edges of an entry act like brackets. They mark where the composition ends and everything between them belongs to the door.
The mistake is moving them inward, tight against the doorframe, where they stop framing and start crowding. Give the entrance breathing room. A door with material pressed against both sides looks narrower than it is, and the display looks like it's encroaching.
Leave the middle open
The floor space directly in front of the door should be clear.
That's partly practical — people have to reach it — and partly compositional. Empty space in front of an entrance reads as arrival. Space filled with pumpkins reads as an obstacle course, and it takes the door out of the composition by burying its base.
Height goes at the sides, not the center
Anything tall directly beside the door competes with the door for vertical attention. Put your height at the outer edges where it brackets, or well back where it acts as background.
The exception is a low, wide arrangement across the base of the entry, which reads as a plinth rather than a competitor.
Consider the door itself
The door is doing half this work, and its color determines what goes near it.
A dark door takes white and pale heirloom pumpkins well; they read against it. A white or pale door takes deeper colors — greens, oranges, dark specialty pieces — for the same reason in reverse. A red door fights orange and gets along with white, green, and neutral straw.
And if the door is scuffed, faded, or has tired hardware, that's the single highest-value thing you can fix before the display arrives. Everything you're about to put on the porch points directly at it.