List the factors of each number
Identify the factors that are common to all numbers
Choose the greatest factor from the common factors
If using prime factorization, break each number into prime factors
Find the prime factors shared by all numbers
Multiply the shared prime factors to get the GCF
If using the Euclidean algorithm, divide the larger number by the smaller number
Replace the larger number with the smaller number and the smaller number with the remainder
Repeat until the remainder is 0
The last nonzero remainder is the GCF