There are a lot of guides out there, but I found this one especially helpful: https://productionadvice.co.uk/using-eq/.

Excerpted below for convenience. Lot more helpful info at the link.

50-60 Hz

  • Thump in a kick drum
  • Boom in a bassline
  • Too much and you’ll have flapping speakers and a flabby mix
  • Too little, and the mix will never have enough weight or depth

100-200 Hz

  • This EQ band adds punch in a snare
  • Gives richness or “bloom” to almost anything
  • Too much makes things boomy or woolly
  • Too little sounds thin and cold

200-500 Hz

  • Crucial for warmth and weight in guitars, piano and vocals
  • Too much makes things sound muddy or congested
  • Too little makes them thin and weak

500-1000 Hz

  • One of the trickiest areas
  • Gives body and tone to many instruments
  • Too much sounds hollow, nasal or honky
  • Too little sounds thin and harsh

2 kHz

  • Gives edge and bite to guitars and vocals
  • Adds aggression and clarity
  • Too much is painful!
  • Too little will sound soft or muted

5-10 kHz

  • Adds clarity, open-ness and life
  • Important for the top end of drums, especially snare
  • Too much sounds gritty or scratchy
  • Too little will lack presence and energy

16 kHz

  • Can add air, space or sparkle
  • Almost too high to hear
  • Too much will sound artificial, hyped or fizzy
  • Too little will sound dull and stifled