You can book the bus either by internet or person. I suggest you do it in person if possible. Book your tip in advance. Only tickets purchased in advance are guaranteed a spot on the bus. The staff speaks good enough English to help you with your transaction. For a directory of buses and other services in Haiti, use FlashHaiti.com
Key things you need to know. If you want to read my experience go further down.
1. Price of ticket is $40 and $30 tax for single trip
2. Price for round trip ticket is $65-70USD and $30 tax
3. They provide food on the bus
4. The Bus arrives between 6-7hrs depending on traffic
5. You will not get world class service but service none the less
6. The morning shift workers will carry your bags to the bus and you do not have to tip, these guys will be wearing red shirts
7. The bus is clean and up to date, no wifi, but has a car charger, toilet, and AC
8. One of the Terra Bus workers exchanges money to Dominican DOP if you require it
9. No ATM at the border so bring cash in case you want to purchase anything
10. They provide immigration/customs cards to fill out for when you get to the DR border and they handle your immigration paper (green paper) from when you entered Haiti
While visiting family in Petionville, I decided to take a vacation in Santo Domingo. Depending on the company, the first bust leaves at 8am and the 2nd bus leaves at 10pm. I decided to use Terra Buses services to get me to Santo Domingo. After we left Petionville, the bus stops at another Terra bus station where the passengers are going through the same process that you went through this morning. These passengers will be added to your bus. While at the station you could use the restroom and buy something to eat and enjoy the nice weather. Please note that the bus does provide food service for you. Around noon they served rice and beans, griyo (pork), and salad, and either water or soda to drink.The Terra bus arrived at the DR/Haiti border immigration around 4.5hrs 12:30pm) after our departure from Petionville. The place looks underdeveloped and unmanaged. Its made up of 3 construction type buildings. Basically an open layout, where anyone could come in and out regardless or not if they are crossing the border. The employees who are traveling with us did not explain what was going on, all they did was give us our passport and told us to get outside. Using common sense, we walked over to the immigration line that said enter and handed the man our passport and the immigration/customs card and received a stamp. As you are doing this, you are bombarded by Dominicans and Haitians who work the area. They are selling drinks, sim cards, chargers, candy, and services to take your bag to the checkout counter. The problem with this whole situation is the employees are dressed like the hustlers working the area, you can’t tell who is trying to help or hustle you. It’s a huge mess of people just walking around and talking in your ear. Unless you are not capable of doing so, I suggest you carry your own luggage to and from the bus because the staff at Terra bus will not help you. If you are strapped for cash, you might want to change some of your Haitian Gourde to Dominican Pesos, they give you within 10 pesos of the actual exchange rate. If you haven’t been to the Dominican Republic and didn’t plan ahead, I suggest you exchange a small amount of cash. As we were leaving, I expected the Terra bus to do a headcount of passengers, they failed to do so. On top of that we received additional passengers.