how to maximise windows in mountain lion like windows 7?
No default option aside from the fullscreen button in the top right corner of some applications. The three colored buttons in the top left of windows also give you some control.

However, there are third party tools available. I found them because I love the snap feature. After trying out a few, I settled on BetterSnapTool because it was the simplest to use and had the most features. Set it to start on bootup and you're all set. I love it.

I don't remember if I bought it in the Mac Appstore or from their website, but the link above is a download from CNet.

Hope this helps. Good luck.