All the above suggestions are excellent.
If expense is not an issue, take Amtrak from New London, New Haven or Stamford to Penn Station, then take the 2 or the 3 train to either Borough Hall or Hoyt St. As suggested, you will need a Metro Card. $10 will be sufficient for the 2 x 2 fares. If you decide to sightsee, you can always put more value on the card.
Should you decide to drive, Saturday morning is almost always decent traffic wise. When driving to downtown Brooklyn, I always come in the back way via Atlantic Avenue. From CT take the I-95 to the Whitestone Bridge.(Possible bottleneck when the New England Thruway becomes the Cross Bronx Expressway just south of Co-Op City. More than likely not on a Saturday morning). Make sure you are in one of the right two lanes on the Whitestone Bridge, then allow yourself to tranistion to the Whitestone Expressway. You will have a couple of miles, but be sure you are in one of the left two lanes, then get on the Van Wyck Expressway. when you pass the unisphere, be sure you are in the right lane so that you can exit to the Jackie Robinson Parkway(used to be the Interboro Parkway). The Jackie Robinson Parkway is narrow in many spots and has some tight curves, especially in the cemetery. The last exit before the end of the Jackie Robinson is Bushwick Ave. Get off at the Bushwick Ave. exit bearing right when you get to Bushwick(there will be a transit maintenance facility directly in front of you when you make the right). At the second(don't hold me to this) light make a left on to Eastern Parkway Extension. Go under the Broadway el, drive on past Fulton, Herkimer, then turn right on to Atlantic Avenue. Very early on, the LIRR is going to come up out of the ground. You are going to be on Atlantic for quite a stretch so take whatever lane is moving best. When you pass Flatbush Ave. then be sure you are in the right lane. You are going pass 3rd St., Nevins, Hoyt, possibly one or two more streets before you get to Smith St. the Brooklyn House of Detention, a high rise jail is on the corner. If you drive past the jail, you've gone too far. Not to worry, though, you are that close to your destination. Anyway, turn right on to Smith St, Smith will become Jay St and Metro Tech is right there.
Partake of Junior's Cheesecake while you are down there.