To factor the expression \( 8m - 24 \) using the greatest common factor (GCF), first identify the GCF of the terms.
- The coefficients are 8 and 24. The GCF of 8 and 24 is 8.
- Next, factor out the GCF from each term in the expression.
\[ 8m - 24 = 8(m - 3) \]
So, the factored form of \( 8m - 24 \) is \(\boxed{8(m - 3)}\).