Or to copy-paste them from the link:
1. Keep It Simple. The flag should be so simple that a child can draw it from memory…
2. Use Meaningful Symbolism. The flag’s images, colors, or patterns should relate to what it symbolizes…
3. Use 2 or 3 Basic Colors. Limit the number of colors on the flag to three which contrast well and come from the standard color set…
4. No Lettering or Seals. Never use writing on any kind or an organization’s seal…
5. Be Distinctive or Be Related. Avoid duplicating other flags, but use similarities to show connections…