Jared Newman writes: “Whenever someone sends me a question about how to fix their Wi-Fi, I wince. It’s not that I dislike helping people with their router problems. But it’s an art that’s hard to conjure without being physically present. Potential points of failure are everywhere. The best I can do is walk your through how I diagnose Wi-Fi problems myself. That way, you can make better decisions on whether (and how) to upgrade your own gear.”