There's a first time for everything, and to make the best of a first time visit to Santo Domingo, it will help to be aware of the following items:

Depending on your country of origin, you may need a visa, passport, or tourist card. In general, United States citizens need either a passport or birth certificate, and a photo document (a driver's licence will do) to gain entrance.  First time (and repeat) visitors should confirm documentation requirements with the nearest Dominican consulate upon arrival.

Foreign currency can be exchanged for pesos at booths to be found at airports, or at major hotels and banks, although Travelers checks and major credit cards are widely accepted. The current rate of exchange is RD$33 to US$1 (double check before departure). Obviously, English is spoken in tourist areas. With visits from over two-million tourists a year, accomodations ranging from high-end hotels to guest houses hosted by locals are available. 

The tropical climate means warm summers, with August being the hottest month, and January, the coldest. Depending on your destination within the city of Santo Domingo, shorts and sleeveless shirts are frowned upon, such as churches, casinos, and some restaurants. Otherwise, light, casualwear is acceptable. It's a good idea to check.  

Santo Domingo is on Eastern Standard Time in the spring, Daylight Savings Time in effect year round, so in the fall, the time is one hour ahead of EST.