Determining And Drawing Possabilities

I already understand how to calculate the possibilities of a combination lock. For example, if you have a combination lock with 4 numbers and each has 0-9 you would use 10 (the number of possibilities you have available on one "wheel") ^ (to the power) of 4 (being the number of numbers on the combination lock). Thus, you have 10,000 possibilities.

Here's is the problem. What is the manual way to do this on paper? I have for my example 3 places on my combination lock so-to-speak EACH number has 4 numbers 1-4. So, ...

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What would be a good way to write each of these possibilities down?

I cannot seem to come up with a good way to do this. Each time I try, I get caught because I cannot come up with a standard way to do this.

Here's what I've go so far ...

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There's not method to my maddness though ... what order should I go through in order to write down all the possibilities?