I'll start. Given any first note in a scale, the fourth note of that scale is either one string up or one string and two frets down. The fifth note is either one string down or one string and two frets up. The circle is completed when you play all 12 notes:
Circle of 4ths, starting with C: C, F, B-flat, E-flat, A-flat, D-flat, G-flat, B, E, A, D, G
Circle of 5ths, starting with C: C, G, D, A, E, B, G-flat, D-flat, A-flat, E-flat, B-flat, F
Hope this helps.