FAQ / [How-to] Bare minimum tune Betaflight

Prerequisite

Recommend test hovering tunes in short increments while checking motor heat. (10 second, 25s, 50s increments.)

Always tune a quad with the same components you expect to fly. (HD Cam, prop-size, etc)
Hardware first – make sure everything firm and secure. no floppy wires, no floppy antennas, etc. no soft-mounting except the FC's gummies. (LiPo straps should not rub gyro, but have flown fine regardless.)
Then tune filters, as per blackbox. For older Betaflight set debug_mode = gyro_scaled, save for anything useful. For 4.5 and later, skip this.
Then tune pids (without feedforward, without dmin/max for step-response analysis)
Repeat Filters and PIDs until no reasonable gains.

Tune filters "first", but i won't go into this here, defaults are pretty good on a 5-inch if you use RPM filtering. If not using RPM filters, then maybe reduce Gyro-LPF-2 to cover the same area (Hz), but it flies either way. When using the latter, typically disable Gyro-LPF-1 if your craft handles it fine. (Maybe even the same for the former, but depends on your craft's noise profile.)

Defaults are for 5 inch quads.
Smaller quads will need higher cutoffs (Hz)
larger quads will need lower cutoffs (Hz)
larger quads will need less i-term due to inherit authority of larger wingspan/propellers.

start with defaults
use sliders
turn off FeedForward (Stick response slider)
turn off D Min/Max (Dynamic Damping slider)
reduce i-term to 0.3 to 0.5 (Drift-Wobble slider)
find a good P/D balance first by adjusting D-Term (Dampening Slider) (with PIDToolbox)
~~increase master multiplier (MM) as needed, but not excessive.~~ (this is potentially mis-information, but still works. see next item)
After finding a good P/D balance, in lieu of MM, raise both P and D sliders in sync, and only as needed, for a more responsive overall system. (preferred rather than Master Multiplier as per @ctsnooze, a Betaflight developer)
return i-term but not excessive (sometimes 0.7 or 0.8 is fine; i don't see a need for more than 1.0 , but that's opinion)
revisit filter/PIDs as needed, but do not chase your tail, at some point there is diminishing returns.
enable FF as desired
maybe enable D/Min/Max again (i don't know enough about this, i know people use it, especially racers to keep motors cool, but my experience i prefer without because i tend to get weird jitters with it [if D-Min is too low].)
Or find presets that match your rig.

Legacy LOS method (PID values no longer applicable, but the general idea does still apply): https://youtu.be/ehyXLsvaEhw