Going to brooklyn on thrusday .........?

HEY GUYS! im going new york on thursday and i will be staying in brooklyn how to i get from broolyn to New york ?? are there trains i can get or busses.. instead of getting taxi's everywhere? will cost me a bomb.. i am staying in the marriott hotel on adams street brooklyn.. and would like to travel to places like... Central Park, 5th avenue, times square?! all that part of new york... but taxi's will cost too much... anyone know some sort of transport that i can get from near my hotel?!?! to them places where i want to go?!?! :D