There is a particular moment in late September when the evenings start drawing in properly, and the first thing you want to do is light something. The mantelpiece is the natural home for that instinct. It sits above the fire, it catches the lamplight, and it is one of the few surfaces in a cottage that is looked at rather than used. Autumn is the season it suits best, because the colours you need are already outside your door.

The trick is to keep it seasonal rather than theatrical. Pumpkins, novelty signs and orange fairy lights can make a sitting room feel like a shop window. A handful of dried stems, a few honest candles and something from the hedgerow will do far more.

Start with the Bones

Take everything off the shelf first, including the things that have been there since spring. Dust it properly, then decide on one anchor piece: a mirror, a small landscape, a framed print, a plain wooden board. Everything else is arranged around that, not competing with it.

Height matters more than people expect. As a rough guide, the tallest object on the shelf should be about two thirds the width of the shelf itself. Any taller and the mantelpiece starts to overwhelm the room; much shorter and it looks apologetic. If you have a picture above the fireplace, leave a clear gap of 10 to 15cm between its base and the tallest item below, so the two do not crowd one another.

Give Everything Something to Sit On

Mantelpieces are shallow and hard, which makes objects look as though they have been abandoned rather than placed. Fix that with a base layer. A shallow tray, an old chopping board, a stack of two or three clothbound books, or a rectangle of slate all work well and give you something to group things on.

A few practical rules that hold for any season:

• Work in odd numbers. Three stems, five candles, one large item with two small ones.
• Vary the heights deliberately, so the eye moves up and down rather than along a flat line.
• Leave a third of the shelf empty. Gaps are what stop an arrangement looking like clutter.
• Push larger items towards the ends and keep the centre lighter, especially if the shelf is above a working fire.

Candles, Handled Sensibly

Candles are what turn a decorated mantelpiece into an autumn evening. Slim tapers in mismatched brass or pewter candlesticks look better than a matching set, and a pair of stubby beeswax pillars on a saucer will burn for hours and smell faintly of honey.

Do keep dried material well away from any flame. Dried hydrangea, grasses and seedheads are effectively kindling, so leave a good 30cm of clear air between a lit candle and anything papery. If your mantelpiece sits low, or you have young children or a cat that treats the shelf as a walkway, use battery candles in a glass lantern instead. Lanterns in particular give you the flicker without the risk, and a warm-white bulb is much more convincing than a cold one.

Light them about half an hour before you intend to sit down. The room will have warmed and softened by the time you arrive with a mug of something.

Foraged Leaves and Hedgerow Finds

Go out on a dry day, ideally after any rain has dried off. Damp leaves will curl and go mouldy within a week of coming indoors.

The best things to look for in a British hedgerow through October are beech and oak leaves on their stems, spindle with its startling pink and orange berries, rosehips, hawthorn, crab apples and the odd twist of old man's beard. Take two or three stems rather than an armful, leave plenty behind for the birds, and never take from a garden that is not yours.

At home, stand short stems in small glass bottles or jam jars with an inch of water, and tuck longer ones behind the frame of your anchor picture so they trail slightly over the shelf edge. A single beech branch laid flat along the length of the mantelpiece, weighted at one end by a candlestick, is often enough on its own.

Dried Flowers and Seedheads

Dried flowers have become fashionable, which means you can buy them, but the good ones are usually grown rather than bought. Hydrangea heads are the easiest place to start: cut them in early autumn, stand them upright in an inch of water, and let them dry slowly in a cool room. They fade to a papery grey-green that looks far better than anything dyed.

Honesty seedheads give you silver discs, teasels and nigella pods add structure, and dried grasses bring movement. Hang anything you cut upside down in a dark, airy room for two to three weeks.

When you arrange them, mix textures rather than colours. Build a base of neutral stems, then add one accent of rust, plum or deep red, and stop there. More than one accent and the shelf starts to look like a display in a garden centre.

Natural, Not Themed

The difference between a mantelpiece that feels autumnal and one that feels themed is restraint and honesty of material. Aim for wood, metal, glass and dried plant matter, and avoid anything plastic. A small bowl of dried orange slices with a few cloves among them will scent the room without a candle, and a single gnarled piece of driftwood or a stone picked up on a walk will hold the whole arrangement down.

Finally, refresh it. Swap out anything that has started to droop every week or so, and add a foraged stem or two as the season moves on. A mantelpiece that changes gradually through October and November always looks better than one set up once and left until December.