Lots of terminal commands come with tab-completion out of the box (start typing a command, hit tab to autocomplete, hit tab twice to bring up a list of available options), or have tab completion scripts you can install after the fact.

Lacking tab completion, any worthwhile terminal commands will at least support a -h/--help flag that will print out a help menu summarizing the different options, or you can open up the man pages to see even more detailed documentation with man [whatever terminal command]. If the terminal command doesn’t have either of those, I’d recommend against using it.