There are a number threads that provide some really good guidance on sights to see, restaurants to eat at, local guides, upscale vss budget hotels, weather, car service, taxi, etc.etc. The search function isn't that great but if you take the time to go back a couple of months, you'll see titles of posts that will correlate to many of the questions you asked.

As a start, a good guide book is the place to start. And get a good map (here is an on-line map
-- http://www.mapmatrix.com/tmhtm/htmtm/02101.html). I would also recommend buying a local sim card(s) as you'll find it useful having a local mobile number.

And weather should be great, and it'll be end of Olympics so hopefully Beijing will settle down.