Some non-obvious tips and lessons I learned[1] from being a reluctant "semi-frequent flyer":
* Most standard "when to arrive for a flight" guidelines are for people for whom missing a flight is catastrophic, so the advice optimizes for 99.9%+ probability of not missing your flight, for people who don't know much about airports[2]. If you're someone who's both used to flying and for whom missing a flight is merely moderately inconvenient (less bad than twisting your ankle) and can be rationally traded off against spending too much time in airports, you should probably be optimizing for more like a 90%-99% chance of making your flight. This can be a big deal in practice! On the high end, I consider arriving 100 minutes before departure time at SFO very "safe" for an international flight, fully 80 minutes faster than the 3 hours guidelines people usually advocate.
* Note that I'm a bit of a klutz, terrible at directions, and not very efficient. I can imagine going down to 80 minutes if you're more reliable than me.
* They no longer print your boarding pass if it's within 60 minutes of an international flight, so you can't go much lower.
* Colorful suitcases: Unusually colorful bags (both luggage and carryon baggage) makes it more likely you notice your bags (saving time), and also makes it more likely other people don't accidentally take your bag (unlikely but very annoying!)
* Carryon only: Relatedly, if at all possible, try to go carryon only. Luggage checkin and baggage claim can easily add an hour to your trip, and it's also inconvenient in other ways.
* Wear a N95 mask, at least if you're easily sick like me: The first two times I flew to London, I got sick both times. A plausible explanation is that I got sick in transit (eg in the airport, on the airplane, or in the bus on the way from/to LHR). So these days I wear an N95 in public transit, at the airport, and in the first and last ~10-60 minutes on an airplane (I think once the plane starts flying
