For Yosemite the advice is similar, though I think you can stay in one place.
Go off peak to avoid the crowds (but if you want to see waterfalls that means spring not fall. The waterfalls are snowmelt and most have run dry by late July)
Book early. We booked over a year in advance. A week later we were told about a niece's wedding that might conflict with our plans. Called back to try to modify and everything but the most expensive place (Ahwahnee) was booked up. Everything is pricier than you would find located elsewhere, but if you stay in the valley, the convenience is great and there is an internal bus system to take you around. We stayed at the Falls Lodge...very good.
Book other activities early. We could not get into some organized activities as they were booked up quickly. There is still plenty to do, but if you have your heart set on a horseback ride you better plan ahead.
Consider the App JUST AHEAD. We got a free trial for Just Ahead when we were at Bryce Canyon in September and it was fantastically helpful and fun. They have guides for many parks, including Yellowstone and Yosemite. It works offline but uses GPS to chime in with information about stuff wherever you are. It's like having your own personal audio guide and would be worth purchasing in my opinion. http://www.justahead.com/
The view from Glacier Point and Washburn Point are the best I have seen anywhere. Sunset would be even better. We enjoyed the relatively easy hikes to Sentinel Dome and Vernal Falls. The sequoias in the Mariposa Grove are nice but from our particular trip's perspective a bit of a letdown. We had just come from Sequoia National where they are more abundant, impressive and less crowded. You are allowed to get up closer to the trees in Sequoia National, whereas in Yosemite they are fenced off from the crowds.
Water bottles are a must as is mosquito repellant! Especially in the El Capitan valley.
We flew into Fresno, a nice smaller and easier to maneuver in airport. Also the drive from Fresno is not only shorter than from San Francisco, but the road is way easier. The winding drive of swithbacks from Yosemite towards San Francisco was one of the more hair-raising we have done.
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