Step 1 : Place the numbers inside division bar:

Step 2 : Find a prime number which can divide at least two of your numbers.

In this example we can divide by 3. If any number is not divisible by 3 write it down unchanged.

Step 3 : Repeat Step 2 until you can no longer divide.

Since there are no primes that divides at least two of given numbers, we conclude that the LCM is a product of starting numbers.

LCM = 3 · 4 · 6 · 2 = 12