Showing that a language is NP Complete (advice)

I am currently getting ready for my final exam in computational models. I know that there aren’t any rules or rule of thumb to show that a language is NP-complete and each problem has its own tricks, but I am really struggling with questions where they give me a language and showing that the language is NP-complete by showing that an NPC problem is polynomial reducible to the given language.

So I wanted to ask for advice. How can I approach such problems? Are there any steps that I can take before to help me somehow? Or is it just literally figuring out which NPC problem is “closest” to the the given language and try to construct a polynomial reduction?

I’d appreciate any advice. Thank you.