I often make the Intro Maker logo a bit bigger than I think looks "perfect" just to accomodoate more logo sizes. The current Intro Maker logo is a bit bigger than a 4:1 aspect ratio, but this graphic can help visualize how your logo will fit inside of it.

Understanding your logo's dimensions (width:height) can help you visualize how your logo will fit inside a template.

The other two most common mistakes I see are using a JPG with whitespace instead of a transparent PNG and leaving too much empty space/padding around the outside edges of a logo. This can make sense when using an image for web or print, but when placed inside of an Intro Maker template this can lead to a smaller-than-expected logo.