On the Gausugonglu of Inner Mongolia (the roads closer to Beijing up to the border with Mongolia), the upper instructions apply.
I hitchhiked around several villages in the western Gobi, using Erenhot as a base. Truck drivers do not expect tips - at least, they did not when I offered money to them. However, private drivers will often request inordinate amounts of money for short distances, so it's best to ask "Doh Shao Chian?", which means "how much?" before getting in.
Chinese is the majority language, especially in the cities. As a Mongolian speaker who only knew a few words of Chinese, people were surprised at me, but pretty accommodating - outside of cities, there is usually at least one person in the room who speaks Mongolian.
You should know that, if you leave the cities, the police WILL detain you here at least once, and you should make according time allowances. In such a case, do not panic - they will actually be very helpful and friendly when they realize you're not a criminal. They will take you to the station, ask you questions, and when satisfied, release you. Have your visa ready, and expect to be asked "What are you doing here?". The whole process takes between one and three hours. Be prepared for this situation, as it happened to me three times in as many days. Consequently, anyone considering hitchhiking here MUST be able to speak enough Mongolian or Chinese to get through this situation.