Writing clean code in C

So how do I do it?
C is supposed to be a good and fast language, but all the programs I make end up being clusterfucks of unreadable code

>>31
x86 assembly is undefined shit.
http://siyobik.info/main/reference/instruction/IDIV
The CF, OF, SF, ZF, AF, and PF flags are undefined.
http://siyobik.info/main/reference/instruction/IMUL
The SF, ZF, AF, and PF flags are undefined.