From the small parking lot, hike 1.1 miles on a well-trodden trail and up the side of the dome to a spectacular view. Take only photos, don't feed the persistent California Ground squirrels, and enjoy the view. Note that the last 0.1 mile up the side of the dome is challenging, but you can go as slowly as you’d like.
TripAdvisor listing: www.tripadvisor.com/Attraction_Review-g61000-d532061
Yosemite NP description: www.nps.gov/yose/planyourvisit/glacierhikes.htm
Yosemite Hikes Description: www.yosemitehikes.com/glacier-point-road/sentinel-dome/sentinel-dome.htm
“Secret” Shortcut to Sentinel Dome This is a wide pullout on Glacier Point Road and is across from a gated service road. It is 0.7 mile past the Sentinel Dome parking lot.
• Map of the road (shortcut trail is on Google Maps!) https://goo.gl/maps/t8DXv1KSxzwLvjg98
• Map view of the Shortcut Parking (I prefer the larger area just ahead on the right): https://goo.gl/maps/vKztu
• Older thread with detailed information about the parking. See Reply 2: www.tripadvisor.com/ShowTopic-g61000-i315-k5661206
Some folks like to combine the Sentinel Dome hike with the Taft Point/Fissures + Pohono Trail hike into a longer loop, but just the Sentinel Dome hike is a great hike for many Yosemite visitors. If you choose to hike the loop, I prefer starting with Taft Point.
In 2022, Glacier Point Road will be closed for the entire year. The road will be moved a bit, parking will likely change, and things will be different. This Sentinel Dome information is only valid for 2021.