According to the population census of 1981 (the last one before breakup), only 5.4% people declared themselves Yugoslav. The census of 1971 that number was even lower 1.2%

Based on that data, and the various personal annegdotes one might easily find, I would conclude that people were primarily thinking of themselves as Serbs, Croats and their respective nations.

Greetings prospective respondents! Many people may have had personal experience in this subject, but just a reminder of which subreddit this is: it's /r/AskHistorians, so no anecdotes or conjecture. Respondents here are expected to have expertise in the subject, offer in-depth information and cite reputable sources. Thanks!

Are you referring to the term "Yugoslav" as in demographics? It was used mostly by people in mixed marriages and others who identified very strongly with the country - about 5% of them at most, according to the census.