Scale by 50% from Specific Side

To increase the size of an object by 50%:

Select an object.
Press Shift then select any control point and drag right on the control point once for each increase.

The object will increase by 50% in the direction of the selected control point.

The image below shows a cube increased to the right on the X-axis by 50%:

Then increased towards the front on the Z-axis by 50%:

To decrease the size of an object by 50%:

Select an object.
Press Shift then select any control point and drag left on the control point once for each decrease.

The object will increase by 50% in the direction of the selected control point.

The image below shows a cube decreased towards the left on the X-axis by 50%: