Sounds obvious, right? But check your windows and doors. Can you see even a sliver of daylight under the front door? That’s a spider highway. Get some weatherstripping from the hardware store. It’s cheap, easy to stick on, and stops drafts (and creepy crawlies).
Next, look at your vents. Those big, dark holes in your floor or wall? Spiders love those. Put a fine mesh screen over them. They’ll hit that screen, get confused, and probably go find a different house. Your neighbor’s house.