Creamy/Milky substance on your oil dipstick.

White dried liquid spots on hoses are a sign of a coolant leak (small or big).

When you open your air box and see a dark greasy stain on your filter.

Coolant leak usually transparent or green and oil leaks

White or greenish substance on your positive and negative battery terminals.

Brake fluid that leaks out of the cap and spreads on the bottle.