A specific starter hike I'd recommend is the Nimitz Way trail from Insipiration Point in Tilden park. What's great about this trail is that - at least if you make it to the end of the pavement at four miles out - you'll get sweeping views of the entire Bay Area, and be inspired for more hikes. The first part is very busy, paved, and even wheelchair accessible, but once you get a few miles out from the trailhead the crowds thin out and the views get better and better. If you like trail running, this is a great place to do it, as there are mile markers to keep track of your distance and pace. And as you'll find out, there really are dairy cows in Berkeley.