Dominicans are friendly and peaceful people. Attempts to speak Spanish are a good sign of respect towards the local population. Be polite, show respect and do your best to speak the language and you will be treated with kindness.
Avoid talking about Haiti. Although relations have improved, many Dominicans, especially the older generations, harbour resentment towards Haitians. Santo Domingo was invaded and occupied by Haiti for much of the 19th century, and the Dominican Republic actually fought its first war of independence against Haiti, not Spain, after which the Dominican Republic suffered several more invasions from its neighbour.
The Trujillo dictatorship massacred tens of thousands of Haitians in the 1930s, fuelling resentment between the two nations. Today, about one million Haitians (a large number given the small populations of both countries) live in the Dominican Republic, most of them illegally. The opinion of some Dominicans towards illegal immigrants from Haiti is similar to the attitude of some Americans towards illegal Mexican immigrants, with the difference that the Dominican Republic, unlike the United States, is a small country, poor by world standards, but still much richer and more stable than Haiti. Gang wars can break out along the border, so stay safe and be sensitive.
Nevertheless, the issues remain very complex and Dominicans often find their position misunderstood by foreigners. For example, the Dominican Republic was the first country to come to Haiti’s aid during the 2010 earthquake and made impressive efforts to help its neighbour during this crisis. This shows that despite their historical, linguistic, religious, cultural and ethnic differences, Haitians and Dominicans still see each other as brotherly but proudly independent nations.
When staying at luxury resorts or other places in the Dominican Republic, it is advisable to tip for most services. The Dominican Republic is still a fairly poor country and tipping the people who serve you helps them to improve their sometimes difficult economic situation.