Electricity
The standard electricity in Beijing is 220 volt.
Credit Cards
Credit cards are accepted in most major hotel aswell in restaurants and shops.
Tipping
In China, they're not used to give tips. In some expensive restaurants you have to pay "service charge" but it will be always specified on the bill.
Price Level
China is generally an inexpensive country. This does not apply to the western and major hotels. Tourist attractions are relatively expensive.