pay and conditions
Wages for teaching in China fluctuate and for the most up-to-date information you should ask around on mailing lists or discussion boards - or just go through a job site with a calculator.
At the time of writing, these are what I would consider average salaries.
Outside of the biggest cities, a private school job teaching 20-25 hours a week should pay from 4000Y upwards, and a quick look through tefl.com seems to indicate that some are starting at 4,500Y or 5,000Y. You should also get a return flight (for a year contract) and accommodation. You may also be offered a few perks like free food or utilities - these expenses are minimal though, and the offer of 2Y's worth of noodles every lunchtime shouldn't really persuade you to take one job over another.
A similar teaching job in the largest cities (certainly Beijing, Shanghai or Guangzhou, and some might include others as well) should get you at least 5,000Y upwards, also with a return flight for a year contract. Accommodation may be provided for you - if not look for an accommodation allowance, and a guarantee that they will help you find somewhere suitable.
Jobs at public insititutions will pay significantly less - subtract 1500 to 2000Y from the above figures. However, working hours should be in the region of 12-16 per week.
Accommodation
The accommodation which comes with your job is usually adequate, if not luxurious, and it can often be very good indeed. Universities tend to have large campuses with plenty of space for building 'foreign expert apartments' and these can often be much larger and well-equipped than you might expect. Worst case scenarios are easily imaginable - think freezing cold, sweltering heat, and 24-hour cockroaches. As always, the same advice applies - get as much information from the school as possible, and then double check it with former teachers if possible.
Holidays
Make sure holiday periods are written into the contract. You should get about a week around National Day (1st Oct) and May Day, along with anywhere between a week and a month at Spring Festival. Summer holidays could be two or three months, or nothing if you are working at a school which runs summer courses during the holidays. Make sure it is clear if you will be paid during these holidays, and also when this money will be payable - teachers prefer to take it before the holiday, understandably, while schools may prefer to pay it after the holiday, just in case you were thinking of not coming back.