Group 1 Group 2 Group 3
Mercury Aries ram
Venus Taurus bull
Earth Gemini twins
Mars Cancer crab
Jupiter Leo lion
Saturn Virgo virgin
Uranus Libra scales
Neptune Scorpius scorpion
Pluto Sagittarius archer
Capricornus sea goat
Aquarius water bearer
Pisces fish
note: Group 1 is not related to Groups 2 and 3.
Groups can be made smaller by having two groups work on the same set.
An example for a mnemonics for Group 1 is:
My viper eats mostly jam sandwiches unless nature provides.