So first of all, this is based on memory, so you are encouraged to check specifics:-

• Kerala is very densely populated but there are no big cities (at least by Indian standards). The coastal side of the state has closely spaced towns and villages. The eastern side is hilly and mostly forested, with a few villages and hill stations.
• Kerala food is different from the usual Indian food, with a lot more seafood, meat, alcohol and Arab dishes.
• Tourists are common in Kerala. No one will mind. And almost everyone can speak English. Kerala has a very good education system.
• Graffiti is common on walls. A lot of this is political, often election related. People take elections very seriously.
• Kochi is the main economic and industrial centre. It has an old fort, a few palaces, India’s only functional synagogue, and good seafood (caught using what are locally called ‘Chinese nets’). The lake and sea are somewhat polluted, so do not go into the water. The famous beaches (Kovalam, Varkala) and lakes (Aleppey) are in south Kerala, and these are popular and somewhat crowded.

Some warnings:-

• Kerala faces floods and landslides during the SW monsoon (June to August). Do not go there during this time.
• Kerala is hilly and has very narrow and winding roads. Travelling by road will take time.
• Less crime than other parts of India, but there are scams. Government-run services (bus / boat, hotels, tourist trips, etc.) are safe.
• Unfortunately some foreign tourists do stuff like carrying drugs or doing immoral stuff with women. While people of course welcome tourists, these are no-nos in India. Do not even joke about such stuff.
• In Kerala, don’t get into political or football-related arguments. People get angry.
• Kerala people, unlike most Indians, are very sarcastic. Pay attention to tone.