Making shit up, so long as it sounds authentic and will pass light scrutiny is okay. With the caveat that you must be willing to change/fix something (or at least defend your decision) if someone calls you on it.

Or leaving out things: the writers of Burn Notice stress that the bombs, etc. that Michael & Co. employ are real, but the explanations always leave out an ingredient or a detail or two so they can't be accused of broadcasting how-to guides for bombers. *G*