By plane.
Sir Robert Falcon Scott always sailed to Antarctica -- the only mode of transport available to explorers at the time.
Your answer depends on your location, your ultimate Antarctic destination, and your mode of transport.
You can transit to Antarctica either by boat or by military airplane.
Ships.
Depending on where you want to go, you can go by ship or by airplane.
Your answer depends on where in Antarctica you want to go, and your mode of transportation, plus the route you choose.
Access to Antarctica is usually by hull-reinforced ship or by long-distance airplanes.
A car
That will depend on your mode of transport
It depends on your point of departure and the mode of transport.
Snowcat and snowmobile, mostly. Flying into Antarctica is common, though ships do sometimes go down towards the ice pack.
The best mode of transportation is walking, because it is 100% "green" (no gas used, no emissions etc.) and because it is excellent exercise. However, if you need to go a far distance, the train is a great mode of transportation as it is rapid, no traffic, and much less expensive than flying.