There are a few ways, depending on where you're coming from.

Plane - Flying into an Airport

If you are traveling from out of state, you can either fly into Boston Logan Airport or the Providence, Rhode Island Airport (TF Green).

If flying into Boston, MA you will either have to book an additional flight (on a very small plane) to Martha's Vineyard, or rent a car/take a bus (2 hr. drive) to the ferry in Woods Hole, MA.  Needless to say, it's much easier to fly into Providence, RI and catch the fast ferry from Rhode Island directly to Martha's Vineyard: www.vineyardfastferry.com

Vineyard Fast Ferry also offers convenient Shuttle Service to/from the Providence Airport through its travel partner Airport Limousine Service; the cost is $15pp. www.vineyardfastferry.com/providence_airport.htm

Train - Taking Amtrak

If you plan on taking the Amtrak, you can easily connect to the fast ferry from Rhode Island directly to Martha’s Vineyard.  Take the train to the Kingston Station (KIN) in Rhode Island www.vineyardfastferry.com

Vineyard Fast Ferry also offers convenient Shuttle Service to/from the Kingston Amtrak Station through its travel partner Little Rest Limousine Service; the cost is $18pp.  You can find easy to read Amtrak/Ferry Schedules and an Amtrak Discount Coupon on their website at: www.vineyardfastferry.com/marthas_vineyard_amtrak_train.htm

Driving - I do not need my car on the island

If you are flying, taking the train or driving from any points west of Rhode Island then Vineyard Fast Ferry will be your most convenient ferry to Martha's Vineyard. They offer advance reservations and dockside parking for $10.00 per day.  You can make reservations on their website at: www.vineyardfastferry.com 

Driving Directions from your location to Quonset Point, Rhode Island Ferry Terminal:

From New York City: Google Map
From Long Island, New York: Google Map
From Boston: Google Map
From Western Massachusetts (Springfield/Worcester): Google Map

When you arrive on the island in Oak Bluffs there are plenty of taxi cabs available to take you to where you want to go.  You can also rent a car from A-A Auto Rental, they are located right next to the ferry dock: www.mvautorental.com 

There is also a great Public Transportation system on the island call the VTA, it operates between all towns about every 30-minyes and is only $1 between towns or $7 for an all day pass. The bus stop is located about only one block away from the ferry dock: www.vineyardtransit.com

Driving - I need my car on the island

Keep in mind that during the summer months Martha's Vineyard can become gridlock with traffic, so if you do not have to take your car you should leave it behind. If you absolutely need your car the Steamship Authority (www.steamshipauthority.com) is the only ferry that takes automobiles to the island. This ferry is located out on Cape Cod in Woods Hole, MA.  You will need to call 508-477-8600 to make a reservation.

Driving Directions from to the Woods Hole Ferry Terminal:

From New York City: Google Map
To Woods Hole - Route I-95 to Providence, RI I-195 East to Wareham, MA Cape Cod, Exit 22A Cape Cod and the Islands to Route 495/25 East, follow across the Bourne Bridge and then follow Route 28 to Falmouth and Woods Hole. Distance from New York City - approximately 270 miles (5+hours not including traffic).  

From Long Island, New York: Google Map
To Woods Hole – Take 495 East to Route 25 East to Orient Point. You will then take the Cross Sound Ferry to New London, CT and hop on I-95 to Providence RI I-195 East to Wareham, MA Cape Cod, Exit 22A Cape Cod and the Islands to Route 495/25 East, follow across the Bourne Bridge and then follow Route 28 to Falmouth and Woods Hole.