1. Bhagawad gita stats with
"dharma-ksetre kuru-ksetre ..."
First word is dharma (complex questions on decision making in life) indicating what to expect from the Bhagawad gita.
2. Ramayana starts with
"tapaH svaadhyaaya nirataam tapasvii..."
First word is tapah (cleansing of personal impurities) indicating what to expect from Ramayana.
3. Yoga sutras start with
First word is atha (engaging with ones life afresh this / each / every moment) indicating what to expect from Yoga sutras.