There are three factors to consider when training for something like Half Dome:
- distance
- vertical gain/loss
- altitude
In OC, you can train for the distance and vertical gain pretty easily. I would suggest checking out the Sitton Peak Trail, the Chiquito Falls Trail, and the Holy Jim Trail to Santiago Peak.
In LA, this loop up Mt Wilson will get you the distance and vertical gain. If you can manage that, then you’re probably ready for Mt. San Antonio (Baldy), which will give you the altitude.
If you’re really feeling ambitious, consider hiking my Six-Pack of Peaks.
These are all longer hikes suitable for a weekend. I would supplement with shorter, more local hikes. Check out our trail guides for variety.