Most methods of fixing warped records of the vinyl variety involve obtaining two 12" squares of glass. Place the record in between them and either leave the package thus in the sun or place it inside a 200°F oven.

These methods both sound risky, and since I've tried neither for any of my warped records (quite a few of which I'd rather keep warped than not at all), I can't recommend these.

How to prevent records from warping is a whole other story.

Some people warp their records on purpose to create bowls or flower pots. They would consider further warping of a damaged record to fix the problem. Don't try to eat out of such a device. There's still that inconvenient hole at the bottom, and all your broth, sauce, or milk will leak out.