You can use the Select Objects pointer (the arrow) and drag a "lasso" around the objects you want to select.

selection lasso

Alternatively:

  1. Click the first object.
  2. Shift+click each additional object.

To select all objects on a slide:

  • Press Ctrl+A (Select All).

To select all but a few objects:

  1. Press Ctrl+A (Select All).
  2. Shift+click to deselect the objects you do not want to include in the selection.