For each scale presented, decide whether it is Major, Pure/Natural Minor, Harmonic Minor, or Melodic Minor (ascending only).
Checking the step between scale degrees 7 and 8 is a fast way to begin narrowing things down, pure minor is the only scale with a whole step between scale degrees 7 and 8. Another good place to check is between scale degrees 2 and 3, Major is the only scale with a whole step there. The difference between a melodic minor and harmonic minor scale is between scale degrees 6 and 7. Knowing your circle of fifths is also very helpful here.