One of the best features of Windows’ user interface is its ability to snap windows to edges of the screen. Mac OS X does not have this capability natively. There are several applications that could do this and all of them are paid applications. Some of them provides just snapping capability and some also provides capability to move windows between screens. After trying a few of them I decided to go with BetterSnap Tool. It has 5 star rating in the Mac App Store. Also it is very cheap when compared to other alternatives.
You could drag windows to edges to snap them, a preview screen will be shown to indicate the window size and position after snapping it. I suggest you to auto start it when your mac starts.
BetterSnap Tool is also keyboard shortcut friendly. I have defined shortcuts to maximise, snap to left, right, top and bottom using cursor with a combination of control, option and command buttons. It is really difficult to find a suitable empty shortcut combination. I have also defined a shortcut to move current window to second monitor. I have gone with maximise on next monitor option, because my second screen’s resolution is significantly lower. If I choose the move to next monitor option window may not fit the available space.