When I open some apps, the window for the app is huge. I know I can resize the window by going to bottom right and corner and using mouse. I was just wondering is there some quicker way using keys etc?
Well, there are some tricks in OS X Lion and above.
Since OS X Lion you can use any window edge for resizing.
If you hold down the option key, you can also resize a window by expanding or decreasing opposite sides of a window at the same time.
If you hold down the shift key while you expand or contract a window, the window will maintain its original aspect ratio.
Also you can combine option and shift.
If you want keyboard shortcuts (not built-in there) you can use 3rd party software like http://www.macupdate.com/info.php/id/26411/mercurymover.
If you don't mind using an add-on, take a look at ShiftIt. It allows you to use keys to move the window to left side, right side, top, bottom, lower left, upper right, etc.
From the dev's website:
If the window is not in fullscreen mode (i.e. where the yellow "minimize" button is greyed out) you can double click the header bar of the window. That will resize it to be the full width of the screen minus the computer's top bar. Then, when you double click it again, it will shrink to the size it was before you first double clicked it.
This way you can, say, have a window occupying one half of the screen, then double click to enlarge it to full, then double click again to go back to the same half.