Grabbing, Scaling, and Rotating
The three basic object operations in a 3D scene are the transformations known (by mathematicians) as translation, scale, and orientation. People who speak Blenderese use the terms grab, scale, and rotate, respectively. Other programs might also use the term move in place of grab or size in place of scale. You can use these three operations to place any object in 3D space at any arbitrary size and with any arbitrary orientation.
Also, because Blender tries to maintain consistency throughout its interface, you can use these transform operations in more than just the 3D View. For example, the same grab and scale operations work when you want to edit keyframes and motion curves in the Graph Editor! How's that for convenient?
In addition to having an emphasis on efficiency, Blender is designed to allow you to work for as long as possible while incurring the least amount of repetitive stress. For this reason, relatively few operations in Blender require you to hold down a key. Typically, you press and release a key to begin the operation. Then you confirm its completion by left-clicking with your mouse or pressing Enter. To cancel the operation, right-click or press Esc. In fact, this keyboard combination even works on some operations that require you to hold down a button. For example, if you try to split an area (left-click and drag a corner widget) and then decide you don't actually want to split it, you can right-click while adjusting the boundary between areas, and the operation stops.