How to procedural generation

You'll want to look at implicit mathematic operations. Specifically, an implicit operation means an equation that will return psuedo-random results given input, but will give the same output if given the same input. As a start, I recommend looking at the following links:

http://catchvar.com/terrain-generation-using-perlin-noise-with-ne

http://notch.tumblr.com/post/3746989361/terrain-generation-part-1

http://stackoverflow.com/questions/4753055/perlin-noise-generation-for-terrain

On Perlin Noise:

http://mrl.nyu.edu/~perlin/noise/

Great paper on Simplex Noise (Type of Perlin Noise):

http://webstaff.itn.liu.se/~stegu/simplexnoise/simplexnoise.pdf

The big hint here is to just futz around with math. There is no out of the box solution. Don't be afraid to press buttons. Don't panic.