For those with a higher budget, or for private groups travelling together, a private transfer between cities and / or in to and out of Torres del Paine is the way to go. A private transfer will go at the times you want and take you door to door.
Rent a Car
For those who wish to have total independence having your own car use is the ultimate winner. You can go where you want when you want. Remember that if you want to take the car across the border a permit is required and this requires about a week’s notice and payment of approx USD120.