As a first time visitor to Oakland on business, where is the best place to stay?

I would recommend staying at the Claremont up in Berkeley, it is pretty nice and you are close to nicest parts of the East Bay in my opinion.

While the Oakland Marriott is the most central and most business-oriented hotel, I suggest you check out the Waterfront Hotel at Jack London Square http://www.jdvhotels.com/hotels/california/san-francisco-hotels/waterfront-hotel. It's a stylish boutique hotel run by the Joie de Vivre group. Jack London Square provides easy access to downtown (it's only a few blocks away), and there's a free shuttle bus up Broadway. There are some excellent restaurants at Jack London Square -- Bocanova, the Forge, Haven, Encuentro, etc., plus Yoshi's Jazz Club, a movie theater, and lovely views of the bay.