1. Conversion factors are fractions that relate units of the same kind and allow conversions between units.
2. To use a conversion factor, write the quantity and original units, then write a fraction with the desired unit in the numerator or denominator to cancel out the original unit.
3. Examples are provided for converting between meters and kilometers, kilometers per hour to meters per second, and grams per milliliter to kilograms per cubic meter using appropriate conversion factors.