When I visited A here in June, I could barely understand the dialect. Moving from Spain's spanish to Caribbean spanish is like living in a new language - even basic words, like juice, change completely when crossing the Atlantic. Slowly but surely I've tweaked my pronunciation: gracias [thank you] is no longer "grathias" and cinco  is no longer "thinco."
Last week I was talking about my dialect struggle to an American english teacher and she blurted out, "What accent? They butcher the Spanish language here!"
--she said it, not me--
In order to help you understand what I mean, and to give castellano speakers a little chuckle, I've written below a few Dominican phrases, followed by the proper (full) spanish phrase. Say them out loud and fast (because they talk excruciatingly fast) and you'll hear what I mean:
Ta to --> Esta todo bien [Its all good, fine]
A po ta bien --> A pues esta bien [its good, its fine]
Mi amol --> Mi amor [my love - term of endearment]
Eh lo mimo --> Es lo mismo [its the same]
Conflé --> Cereales [derivative is Cornflakes, but used for cereal in general]
And my all-time favorite...
Ya tu sabes [you already know] - use this whenever you're having a conversation and you're too lazy to explain your point. Use approximately once every 30 seconds of speech.