I am sometimes confused about whether to put the in front of a noun or not, so to solve such dilemmas, I have come up with the following strategy.

When in doubt, whether to put the in front of a noun, try to think of cases where you would put a/an in front of that noun. If you can't find it, there is no way you would need to put the, but if you can find it, then consider whether you are talking about a specific case of that noun (for example, a specific apple in a group of apples).

For example, just 5min ago, I have thinking whether to put the or leave it blank to the place of X in the following sentence.

[...] along X y-direction.

Eventually, I leave it blank beucase I thought I would never say something like along a y-direction (I am not sure whether it was correct to that), but my question is

Question: Is this strategy correct? Is there any example of whether that would fail? and if so, do you have any other strategy that one can use in such situations?