Direct answer
You should know entry requirements, safety basics, local customs, money and transport options, best times to visit, and a few practical tips to enjoy the Dominican Republic safely and respectfully.
Visa / Entry requirements
Best time to visit
Safety tips
Local customs & etiquette
Currency & money
Transportation
Must-know tips & local insights
Final practical checklist
Have a great trip—if you tell me your arrival city and travel dates I can give more specific advice (weather, events, neighborhood safety, and transport options).