I once saw bra patterns in russian for free on the internet, but now I can't find them anymore. I think it would be easiest to buy yourself a pattern. bra's are not just something

, and patterns don't cost over $10 or so I think. That's not too expensive if you think of what a bra would cost

..
here you can find several bra-tutorials with pictures. they are in german, I know, but maybe the pictures will be enough

.
this one is about copying an existing bra (although I think you must rip apart the existing one for the sake of creating a pattern).
to help you understand: BH means bra, bugel means underwire, spitze means lace and elastik means elastic (now that last one was difficult).