Keeping pictures and artwork in proportion.

When resizing elements in PowerPoint, you want to size them so that all the elements remain the same size in relationship with each other. You can do this by making sure that when you're resizing something, that you are resizing everything at once.

For example, if you have four pictures that you have to resize, but they have to stay the same size in relation to each other:
You click the first picture.
Hold down the Shift key.
Click the other three pictures.
Release the Shift key
Then you mouse drag the picture to the size you want.