I am from Malaysia and plan to visit Guangzhou and Shenzen sometime in December 2014.

A single entry is enough. If you are visit for business, then the correct type should be F or M with invitation letter. If for tourism, a tourist L is enough showing round-trip ticket and hotel bookings. Keep in mind that a single entry one is valid for 3 months only, so do not apply too early. You can apply in late October or November 2014 of you plan to visit in December.