I'm using InDesign cc 2015 and can't seem to get the hang of appropriately resizing images (ie without making them look short and fat or long and thin) within the frame of a page. Any tips on how I can do this?
Try holding shift key while strerching one of the image's corners. Add Ctrl to stretch image with frame... that should work.
In addition to what JanCE said, select the frame and try out the fitting options in the Object menu.
More details here: Work with frames and objects in InDesign .
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