I am a U.S. citizen planning a trip to Mainland China (Suzhou and Qingdao) in July 2018. How early can I apply for a tourist visa? If I buy my airplane tickets in January, will I be able to apply around that time? I already made hotel reservations.
Once you have everything for the visa application – plane ticket, hotel reservations, travel insurance (that one isn't required by all Chinese consulates, check whether you need it or not with them) – you can apply for it any time you want. One of the boxes to fill out is the date you are planning to enter China. That's the date they will take into consideration.
However, my lengthy experience with Chinese consulates shows that the visa section doesn't always listen too good. They could decide to issue the visa with a starting date of the day they approve the visa. Which, with a validity of 3 months for a single-entry visa, would play havoc with your plans.
My advice is to check with them (or the travel agency you're using) directly. I only go through travel agencies for China visas, as they usually take care of everything, and the extra fee is usually well worth it.