If you want to make really easy ... contact the hotel and have them send a car to pick you up. Highly recommended if you don't want an (mis)adventure upon arrival.

Make sure that the concierge writes down where you are going. I made the mistake of simply telling the doorman where I wanted to go and the driver took me to my CO HQ. Apparently the driver saw the company name on my shirt or briefcase. It took a number of phone calls before I finally found someone who could explain to the driver where I needed to go.

Taxis in Beijing vary in price... with the cheapest being flea ridden and having no A/C.

The top end taxis are hard to find but are worth the slightly higher expense.
If I recall correctly: 1.40 RMB no A/C, 1.80 RMB for A/C, 2.40 RMB A/C large car. Many taxis will have a sign saying something about having been flea-bombed... Skip the 1.40 RMB taxis unless you like fleas & smog (open window AC -- and beijing is on its way to being the next Mexico City!)

Unless you are travelling from city center to the outer ring road during rush hour a typical 1.80 RMB taxi fare around town will run about 10-14 RMB (or < $2 USD). Taxis are cheap and plentiful -- making them the easiest way to get around. There is also a subway line but we didn't need to use it.