I have used a company called Thames Consular (now CIBT??), they offer a very good service and fast too.

Are you going on Business? If so you will need a business visa which has a different criteria.

You will need one photo to be stapled onto the form, you can download the form from CIBT's website (google them) the website will also tell you all the supportings docs that you need.

double entrance is a little more money but it is worth it for the flexibility (say if you are heading to HKG).

You can also get 1 and 2 year multientrance Visas but you need 3 entry stamps in your passport (I think) before you will be able to apply for one of these.

Hope that this helps.