I want to buy tickets for the 2008 Olympic games in Beijing.  How can
I get them for 8 people in specific events?

as i know you can only preorder them:
http://travel.ec-t.com/citytravel/olympic_main.aspx

Normally ticket sales for the Olympic Games commence two years before
the event is due to take place so I think you'll have to wait a while!

The procedure for Beijing olympics is far from started yet. I will
give you the procedure folloed in Athens olympics which I think will
give you a pretty good idea of what to expect.
1) The first round of pre-booking started 14 months before the games ,
was through internet and was open only to EU residents. There was a
limit for some categories of tickets. If in some categories there was
overbooking, a lottery was held automatically by the system.
2) After this first stage and about 9 months before the start of the
games sales was made through the same electronic system or from the
official bank of the games  until the end of the games
3) about one month before the start of the games special selling
points were opened.
I expect a similiar procedure to be followd by beijing as well/