Here's the official ticket office for hte Chinese Grand Prix:
to order by phone: 86-21-63336201/63336203 (9:00 AM to 16:00 PM, Monday to Friday Beijing Time)
to order online:
www.icsh.sh.cn/english/shang/tickets_f1.htm - This is how I ordered by tickets for the past few years.
You can find more information at:
http://www.icsh.sh.cn/english/shang/main.php
or you can email them at:
ticket@ics.sh.cn
There are usually tickets available but the good seats are usually gone.
I would recommend sitting in the Main Grand Stand (you can see most of the track and most importantly the pit) or Grand Stand B area (at the end of straight way and turn 1-3) - b/c you'll see most of the passing and incidents. I've always sat at Grand STand B area (this year hopefully I will have hospitality suite seats)
As for discount, I doubt it will be substantial and the discount tickets are usually crappy seats. Hotel tickets are usually rip offs b/c the concierge charges a 5-10% mark up. Also be VERY CAREFUL of counterfeit tickets - they usually are "Too Good To Be True Deals".
Just to be safe, I would order the tickets now. This way you will get the tickets in May/June (they will mail it to you) and you have nothing else to worry about.
One thing you DO need: if traveling by private car or if you have a chauffeur - it's the parking pass. without that, you will be walking 3 miles to the closest pickup location (NO JOKE). If you are traveling via hotel's shuttle bus, then you don't have to worry about this.
Good luck and maybe i'll see you at the race.