Autumn offers a very wide range of materials to use in arrangements, from seed pods and nuts, mosses and fruits, to leaves, berries, and many different flowers. The way to approach using them all is simply to treat the material as you would any ordinary flowers and foliage; very few will need special treatment.
Small things such as nuts may need to be glued to a stem made of wood or stiff wire. Wooden food skewers easily and then added to an arrangement. Some seed heads such as clematis with their light fluffy strands may need to be sprayed with a fixative and varnish of some kind to hold them together. A few other ingredients can also benefit from this treatment, Iris foetidissima pods in particular, otherwise, the berries fall out as they open up and dry.
Most berries branches will last well in water as many have to remain like this in the wild with leafless stems for months until the fruits are eaten by birds and the seed distributed. Colored autumn leaves on trees and shrubs are a little trickier to handle as the leaves are often on the point of dropping when their colors are at their most brilliant and useable. Treat them gently when getting them home, then once they are in an arrangement their leaves may drop gradually over a few days. A mist of hairspray or fixative may help, aimed where the leaf stem joins the branch.
Containers for autumn ingredients can be really rustic and countrified so baskets and wooden containers of all types work well. Here a collection of pale and split wood baskets and boxes are linked by their soft texture and color and look just right with the rich brown papery oak leaves and brilliant physalis lanterns. Line baskets and boxes with plastic to make them waterproof or stand a container inside.