Update Feb 2023: Removed tip about WiFi 6. Added tip about 5GHz Channel 165. Disclaimer for WRT1200AC WiFi issues.

All these tips are true, at least to the best of my knowledge. However, these tips gets wackier as the numbering increases! Beware!

0. Use a wired connection when possible. Not only does this free up the WiFi spectrum for other devices, but Ethernet gives you a much more reliable and speedy connection.

1. A well-known tip: use your 5 GHz network for better speed and latency. The 2.4 GHz spectrum is polluted with noise sources such as microwave ovens, wireless security equipment, and other neighbouring 2.4 GHz WiFi networks. Keep in mind that the range of 5 GHz WiFi is shorter, so use the 2.4 GHz strictly for long-range and non-latency sensitive devices, i.e. IOT devices, older WiFi devices, and rarely used devices.

2. Broadcast your 5 GHz and 2.4 GHz WiFi networks on separate SSIDs. Some older WiFi guides recommend running them on the same SSID, but this means that the operating system will decide on which network to connect. It's safer to take control of the network selection, and reserve the 5 GHz for your main devices such as your laptop and smartphone. You can simply disable "Connect Automatically" on the 2.4 GHz network to keep it remembered.

3. macOS's AirDrop feature creates massive latency spikes on WiFi: [0, 1]. To disable it, set AirDrop to "No One" in Finder, then run sudo ifconfig down awdl0. I found latency on 2.4 GHz networks improved significantly. Currently, I run the command automatically through BitBar, and I added the following to the end of my /etc/sudoers file: yoonsik ALL = NOPASSWD: /sbin/ifconfig awdl0 down to bypass sudo prompts.

4. Lower your WiFi radio power. Seriously. Check out 8 reasons to lower WiFi power by Metis Oy. I've frequently run into situations where the WiFi indicator says full strength, but the Internet isn't working. Too high of a power setting can cause this. This tip is especially important for smartphones, which are constantly on the move.

5. Set your 5GHz network to Channel 165 to improve network latency and decrease jitter. You will notice an improvement with real-time communication and gaming. Most routers don't use this channel due to the narrow 20MHz bandwidth which reduces speeds to ~150Mbps. For the best of both worlds, set up two access points on 5GHz, one for high throughput, and the other for latency sensitive applications.

6. Try to find a router that has rotatable antennas. If there are two antennas, rotate them so that one is vertical, and the other is horizontal. If there are three, rotate them so that two are vertical (angle these two very slightly away from each other), and the last one is horizontal. Imagine a doughnut radiating from the horizontal antenna, and choose the horiontal angle so that the doughnut circumference points to common areas.

7. Use a router that can run OpenWRT. I recommend the Linksys WRT1200AC, which is a dual-core ARM router capable of NAT and SQM shaping at Gigabit speeds. Unfortunately this WiFi chipset is unstable under load, so I use a x86 OpenWRT machine and the Atheros AR9462 card for home wireless. OpenWRT allows you to change WiFi settings such as radio power and lets you install custom packages.

8. Use proper antennas. This means don't buy the goddamn 18dB antennas off of eBay! Antennas aren't magic, so the higher the gain (dB), the narrower the radiated field. This means that the WiFi range will only improve at a very specific angle, and become worse in all the others. Instead buy regular dipole antennas with a 2 or 3 dB gain.

9. Dual-band antennas are strictly worse than their single-band counterparts. If your router combines the output of both WiFi channels into a dual-band antenna, disable one of the channels and attach the proper single-band antenna. I disabled the 2.4 GHz network on my WRT1200AC, and switched out the antennas for 5 GHz 3dB ones from Data Alliance. I then set up a 2.4 GHz network on another router, and installed good quality 2.4 GHz antennas.