There are 4 entrances into Yosemite National Park.
If you are coming from the Bay Area or staying in Groveland, you will most likely be using the Big Oak Flat entrance on HWY 120 East. This allows easy access to Tioga road, the valley, and Hetch Hetchy.
Arch Rock entrance on HWY 140 is in the middle and allows easy access to everything.
The South Entrance on HWY 141 is the best entrance if you are coming from Los Angeles area. There are lots of curves coming down this road, but one of the benefits is that your first view of the valley will be Tunnel view.
If you are coming from the east, you will most likely be using the Tioga Pass Road on HWY 120. This road does close during the winter, so make sure to check if it is open before you leave.