Here's a REALLY HELPFUL TIP!

Okay you know how sometimes you paste or add layer and the image is kinda' real big?  (and we can use Lucies tv in the above post as an example...) so you grab the handle points and you resize it down and hit the apply button.  Oh man! you made it too small! now if you select it and resize it upward, it's all fuzzy and looks like crap. This is because whenever you transform the image you are destroying pixel information. your only option is to re-import the layer/image are try to get it right the first time...

This time BEFORE you resize it, select the layer and from the layers palette (click the little arrow by the tabs) scroll down and select CONVERT TO SMART OBJECT. This will keep the layers graphic at the imported resolution (or size) and allow you to resize it smaller and then if you change your mind and found you went to small, you can resize it upward again without any loss of clarity. 

 I work with SMART OBJECTS all the time. Great time saver when trying out different comping ideas.