user25567: For the life of me, I can't tell what I'm doing wrong, but here we are!
I am on Mac, newbie on After Effects. I can scale anything (not proportionally) with the click on a corner but, unlike in Indesign or Illustrator, Shift + click just does not work! It kind of releases the frame, just like if I had clicked outside of it. 
I am on Mac, After Effects CC. I verified the following:

Shift is pushed (the "non permanent capital letter" key of the keyboard)
Mode is "Selection tool" (the arrow)
I am indeed clicking on a corner (where little square appears) and not on the side!

Yet it just deselects the whole thing and making me crazy! What am I missing?

user4426: When I hold down shift, images and shapes scale proportionally. Just grab a corner handle and drag. 
Alternatively:
Select the layer, press S to reveal the Scale parameter. Adjust that value. It will be proportional unless you unlink the x and y scales. 

25567: <p>For the life of me, I can't tell what I'm doing wrong, but here we are!</p>

<p>I am on Mac, newbie on After Effects. I can scale anything (not proportionally) with the click on a corner but, unlike in Indesign or Illustrator, Shift + click just does not work! It kind of releases the frame, just like if I had clicked outside of it. </p>

<p>I am on Mac, After Effects CC. I verified the following:</p>

<ul>
<li>Shift is pushed (the "non permanent capital letter" key of the keyboard)</li>
<li>Mode is "Selection tool" (the arrow)</li>
<li>I am indeed clicking on a corner (where little square appears) and not on the side!</li>
</ul>

<p>Yet it just deselects the whole thing and making me crazy! What am I missing?</p>
 4426: <p>When I hold down shift, images and shapes scale proportionally. Just grab a corner handle and drag. </p>

<p>Alternatively:
Select the layer, press S to reveal the Scale parameter. Adjust that value. It will be proportional unless you unlink the x and y scales. </p>
