Make your home harder to ignite

Your yard keeps the fire back. The house itself has to stand up to embers. Start at the top and work down. Many of these fixes cost little; others are worth doing when you replace something anyway.

Roof

Replace missing or loose shingles so embers can't get in under them.
Keep leaves, needles and other debris off the roof. Roofs catch embers, and debris gives them something to burn.
When you replace a roof, ask for a Class A fire-rated roof, the rating that protects best. Asphalt fiberglass shingles, clay and concrete tile and some metal roofing are Class A.

Gutters

Clean them out at least once a year, before fire season, and again if they fill up. Embers can light gutter leaves and set the roof on fire.
Gutter covers keep leaves out. Choose metal ones, or another material that won't burn.

Vents

Cover attic, roof and crawlspace vents with metal wire mesh with openings no bigger than 1/8 inch. It keeps embers out and still lets air through.

Walls, eaves and windows

Siding and skirting that won't burn, like fiber-cement or stone, holds up best. Burning siding can carry fire inside the walls and into the attic.
Close in open eaves with material that won't burn; embers and heat collect under them.
When you replace windows, choose tempered or multi-pane glass, which holds up to heat better. If heat breaks a window, embers and flames can get inside.

Decks and porches

Sweep leaves and needles off and out from under the deck.
Don't store firewood, lumber or anything else that burns under a deck. Things stored under a deck can catch fire and burn the deck.
Keep plants, bark and anything else that burns out from under the deck.

Fences and gates

Replace the section of wood fence that touches the house with metal.

A wood fence that touches your house is a fuse that leads to the wall. If it catches fire, it gives the house a flame that keeps burning against it. Make the fence and gate within 5 feet of the house metal or another material that won't burn, and keep leaves from piling up along the bottom of any fence.

Sources

Why each step matters: NFPA, IBHS Wildfire Prepared Home, Oregon home hardening guide (Building Codes Division).
Loose or missing shingles, cleaning roofs and gutters, metal gutter covers, 1/8 inch metal mesh on vents, fiber-cement or stone siding and skirting, clearing under decks, metal gates within 5 feet: Oregon State Fire Marshal, Oregon Defensible Space.
Fencing within 5 feet of the home, including where it attaches: IBHS Wildfire Prepared Home, research.
Class A roofs and which materials are Class A: Oregon Building Codes Division, home hardening guide (PDF).
Enclosed eaves, tempered or multi-layered glass, 1/8 inch vent mesh, gutter guards that won't burn: State of Oregon, home hardening one-pager (PDF).
Gutters kept clear and the area under decks kept clear: IBHS Wildfire Prepared Home.