A loop plays, then again with one frequency boosted. You find where on the spectrum the boost was. This is the core skill behind every EQ decision: knowing what 200 Hz, 3 kHz or 10 kHz sounds like without sweeping around first.
At level 1 the boost is +10 dB with a wide bell, somewhere between 120 Hz and 8 kHz, and you have about an octave of margin either side. By level 10 it's +2 dB with a narrow bell anywhere from 50 Hz to 16 kHz, and the margin drops below a tenth of an octave.
Anchor a few reference points first (the low end around 100 Hz, the 'boxy' zone around 500 Hz, presence around 3 kHz, air around 10 kHz) and locate everything relative to them. Big boosts first, then smaller ones.
Added energy is easier to notice than missing energy. Boosts teach you what each region sounds like; cuts, which are harder, test whether you really know it.