The eight PLANETS by size. JUPITER, SATURN, URANUS,NEPTUNE, EARTH, VENUS, MARS and MERCURY. Pluto, the dwarf planet isn't included. Let us say we are going to have a test on these eight Planets, so memorize them. J & S, JUPITER & SATURN. Think of them as Bowling Balls. Next:
U & N, URANUS & NEPTUNE. Think of them as Billiard Balls.
E & V,EARTH & VENUS. Think of them as small Marbles. and finally,
M & M, MARS & MERCURY. think of them as Tiny Peas.

It works for George Gebhardt, the author. See how lquick you can memorize the 8 Planets that revolve around our SUN. Eightly or better is a passing mark.