4 ways:

1) Sign treaties with other nations to explore oil there. But it maybe too late. Americans have gotten hold of almost all rich oil resources worldwide. Sudan is a possibility but even engaging Sudan is now branded as helping massacrer government in Sudan by the US and Europeans.

2) Sign treaties with Russia, build pipelines from Syberia to China. At least, in this way, China may be able to get cheaper priced oil. And probably buy them without using USD.

3) Find oil locally. But that's not very hopeful. China is not a oil rich nation, unfortunately.

4) Develop nuclear power capability to eventuall supplement or replace crude oil.

However, for now, China has to spend 7 times more money to buy them from the Saudis on open market. Well, when China pays Saudis, the money will end up in US' pocket sooner or later.